To provide an authentication card magnetizing method capable of making an authentication card managing machine reduced in depth, namely thin in thickness and to provide the machine.

This authentication card managing machine 1 which writes by magnetization data which enable the opening/closing lock attached to a safe deposit box door to be unlocked on an authentication card 5, having magnetization points 5a arrayed into a matrix form is so structured that the authentication card 5 is conveyed intermittently, and the data are written in order to the magnetization points 5a of the authentication card 5 by an encoder 14 having magnetizing heads 14a in single array direction at right angles to the conveyance direction of the authentication card.