A method for manufacturing an optical electrical module includes steps as follow. Forming first patterns on a first substrate by a first mask, wherein an angle between a primary flat of the first substrate and an arrangement direction having a maximum number of first pattern units of the first mask is (θ+90°*n), wherein θ is between 22° to 39°, and n is an integer. Subjecting the first substrate to a first patterning process using the first patterns as a mask to form accommodating grooves and a reflective groove connected with the accommodating grooves in the first substrate, wherein an extension direction of each of the accommodating grooves is perpendicular to an extension direction of the reflective groove.