A biometrics authentication apparatus and a biometrics authentication method are disclosed. The biometrics authentication apparatus includes: a light source configured to emit a light; a modulator configured to change a spatial distribution of the light that is scattered and reflected from a region of interest of a user; a detector configured to detect an integral power of the light that is scattered from the region of interest; and a processor configured to obtain a measurement signal based on the integral power of the light, compare the measurement signal with a reference signal stored in a memory, and determine whether to authenticate the user based on a degree of match between the measurement signal and the reference signal.