Provided is a multi-beam semiconductor laser designed to change a pitch between laser beams while eliminating the risks of crosstalk and power-down. Reflective mirrors are disposed at either end surface of the laser oscillating region in the active layer formed along the striped current path, a reflective mirror located at a front surface has a reflectance sufficiently high to prevent emission of a laser beam from the front surface, and a wavelength demultiplexer is disposed at a location in each of the plurality of laser oscillating regions so as to change the direction of propagation of only laser oscillating wavelength beams for emission from the laser oscillating regions. The above construction allows adjustment of a pitch between laser beams.