1. A method for searching a gene sequence, the method comprising: on a gene sequence search apparatus, receiving the gene sequence from a user; generating extended sequences of the received gene sequence, partial sequences included in the gene sequence and an inverse sequence complementary to the gene sequence; storing the gene sequence, the extended sequences, the partial sequences, the inverse sequence and input-related record information in a database; performing an integrated search using an integrated search server by inputting the gene sequence to the integrated search server; estimating a gene sequence search ranking of a first predetermined period, wherein the estimating is performed using the database; integrating and storing an integrated search result of the gene sequence and a gene sequence search ranking result in the database; and outputting the integrated search result of the gene sequence and the gene sequence search ranking result to the user.