1. A category classification processing device comprising: an example storage unit configured to store Q&A (questions and answers) examples including pairs of questions and answers; a log storage unit configured to store search keyword logs relevant to searching the Q&A examples; a search unit configured to send, to a terminal device, an input screen image used for inputting one or more keywords, search the example storage unit by using the one or more keywords input to the input screen image and extract Q&A examples based on the one or more keywords, send identification information items expressing the extracted Q&A examples to the terminal device, and store, in the log storage unit, search keyword logs including the identification information items relevant to the Q&A examples which are actually referred to at the terminal device with the use of the identification information items, the identification information items in the search keyword logs being associated with the one or more keywords input to the input screen image; and a category extraction unit configured to obtain keyword storage frequencies expressing a number of times each of the keywords, which are recorded together with the Q&A examples in the search keyword logs, is stored for each of the Q&A examples, extract, as category candidates of each of the Q&A examples, an m number of top keywords (m being a positive integer) in a descending order of the keyword storage frequency, use the extracted category candidates as categories, and associate the categories with the Q&A examples.