A storage device for generating an identity code and an identity code generating method are disclosed. The storage device includes a first storage circuit, a second storage circuit and a reading circuit. The first storage circuit stores a plurality of first data and the first data have a plurality of bits. The second storage circuit stores a plurality of second data and the second data have a plurality of bits. The reading circuit reads the second data from the second storage circuit to form a first sequence, selects a first portion of the first data according to the first sequence, reads the first portion of the first data from the first storage circuit to form a target sequence and outputs the target sequence to serve as an identity code.