An optical transmitter has a case. The case houses a laser beam generator, a lens, a cooler, and a high heat conductivity member. The lens concentrates the laser beam generated by the laser beam generator and leads the laser beam to an optical fiber. The high heat conductivity member is arranged between the laser beam generator and the lens and the cooler. The laser beam generator has higher heat conductivity than that of the case. The laser beam generator conveys the heat generated in the laser beam generator to the cooler.