An optical module is formed of a first optical block and a second optical block each equipped with a lens the optical axis of which needs to be aligned, the blocks being positioned and secured to each other, and has stepwise positioning means. A positioning means includes spring pieces each having an abutting slope, and edges. Four spring pieces are formed in the second optical block such that their abutting slopes are disposed at four corners of the second optical block. Positioning is implemented when the abutting slopes meet the edges of the first optical block. Another positioning means includes a depressed part and a guide slope formed in one of the two optical blocks and a raised part formed in the other optical block. The raised part is fitted into the depressed part.