A forged-physiological-characteristic filtering device includes: a physiological characteristic scanning circuit for conducting a plurality of times of physiological characteristic scanning operations; a control circuit for acquiring a plurality of unverified-user physiological characteristics and generating a plurality of corresponding unverified-user action records, and for calculating time interval between two consecutive unverified-user physiological characteristics to generate corresponding unverified-user time interval records; and a secure circuit for respectively comparing the plurality of unverified-user physiological characteristics with a plurality of valid-user physiological characteristics, for respectively comparing the plurality of unverified-user action records with a plurality of valid-user action records, and for comparing the unverified-user time interval record with a valid-user time interval record. The secure circuit is allowed to conduct encryption, decryption, or signature operation on data transmitted from a host device only if all of the above comparing operations match with predetermined conditions.