A user terminal includes a diagnosing unit 23 conducting a password diagnosis based on a password trial; a recording unit 24 recording time related to the password diagnosis; an information acquiring unit 21 acquiring the time related to the password diagnosis of the last time, which is recorded by the recording unit 24, as the time of last diagnosis and acquiring reference time for determining whether the password diagnosis is required or not; and a determining unit 22 determining whether or not the time of last diagnosis conforms with a predetermined condition with the reference time serving as a benchmark, wherein the diagnosing 23, if the determining unit 22 determines that the time of last diagnosis conforms with the predetermined condition with the reference time serving as the benchmark, performs the password diagnosis.