1. A method for searching a gene sequence, the method comprising: receiving the gene sequence from a user; generating extended sequences including 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; integrated-searching the gene sequence using a gene sequence search server; estimating a gene sequence search ranking for a first predetermined period using the database; and outputting an integrated and searched result of the gene sequence and a gene sequence search ranking result to the user.