To provide a personal authentication method and a personal authentication system capable of authenticating that a user of a credit card is the owner of the credit card.

When the user of the credit card purchases merchandise, data of the credit card is sent to an Internet shopping site 3. The Internet shopping site 3 inquires about propriety of usage of the credit card to a site 2 of a credit card company. The site 2 of the credit card company accesses to a personal authentication site 1 and requests for authentication of whether or not the user of the credit card is the owner of the credit card. The personal authentication site 1 authenticates whether or not the user of the credit card is the owner of the credit card on the basis of personal authentication data input by the user of the credit card using a terminal 4 of the credit card user.