1. A program retrieval support device that searches accumulated TV programs for a TV program, said program retrieval support device comprising: a program-information-accumulation unit including a memory in which pieces of program information are accumulated, each respective piece of program information being related to a corresponding TV program; a search-criterion-input unit configured to receive, from a user, a search criterion for a program search; a program-information-search unit configured to search the pieces of program information accumulated in said program-information-accumulation unit, using the search criterion received by said search-criterion-input unit; a program-information-display unit configured to display found pieces of program information in a list, the found pieces of program information being found by the search performed by said program-information-search unit; a program-information-user-selection unit configured to receive, from the user, an input of selecting a selection piece of program information from the found pieces of program information displayed in the list by said program-information-display unit, such that the selection piece of program information is selected using the input received by said program-information-user-selection unit; a major-program-determination unit configured to (i) determine whether or not the selection piece of program information has a commonality with the found pieces of program information found by said program-information-search unit, based on a common keyword included in (a) a program representative keyword set and (b) a search result basic keyword set, the program representative keyword set consisting of words included in the selection piece of program information, and the search result basic keyword set consisting of words selected from words included in the found pieces of program information, and (ii) determine, based on a result of the determination regarding the commonality, whether or not a TV program corresponding to the selection piece of program information is a major program; a program-search-criterion-generation unit configured to generate a new search criterion for narrowing down the found pieces of program information to be more similar to the selection piece of program information, when said major-program-determination unit determines that the TV program corresponding to the selection piece of program information is the major program; and a program-search-criterion-display unit configured to display, to the user, the new search criterion generated by said program-search-criterion-generation unit, the new search criterion being used as a search criterion candidate for the user to potentially be received by said search-criterion-input unit as a next search criterion for further program search, wherein said major-program-determination unit is configured to determine that the TV program corresponding to the selection piece of program information is a major program, when the program representative keyword set includes the search result basic keyword set and there are a predetermined number or more of common keywords between the program representative keyword set and the search result basic keyword set.