On a two-dimensional optical identification device with same gray level, a plurality of two-dimensional optical identification codes are arranged, each having a plurality of data blocks and an outer positioning block. Each data block has a plurality of defined patterns, and each defined pattern is located in one of virtual areas produced by equally dividing the data block. The outer positioning block has a plurality of first positioning points and a first direction identification point, and is placed at two adjacent boundaries of the plurality of data blocks for defining the positions of the plurality of data blocks. A fixed position data block is selected as a data block coding indication block for indicating the coding of the other data blocks.