It is an object of the present invention to realize a low cost laser light source capable of emitting several mW optical power while the operation current is reduced. In particular, the present invention concerns a 1.3 μm wavelength band laser device suitable for several to several ten km short distance fiber optic transmission and also a less power consuming optical communication module in which such a laser is preferably mounted. As a laser structure which eliminates the necessity of adding an optical isolator by providing improved immunity to reflected light while lowering the operation current for less power consumption and not lowering the response speed, a short cavity laser which operates in multiple longitudinal modes is introduced. Especially, an angled mirror structure is formed at the laser's emitting edge to change the optical output direction so that the light is emitted from the top or bottom of the substrate.