A semiconductor laser device has a heat sink of which multiple laminated plates are constituted and a semiconductor laser element mounted on upper surface of the heat sink. The heat sink has a channel in which a coolant flows inside thereof. The heat sink includes a channel-forming plate portion that forms the channel and a mounting plate portion that forms an upper surface of the heat sink that comes into contact with the channel. The mounting plate portion is made of material having a thermal expansion coefficient, which is closer to that of the semiconductor laser element than that of the channel-forming plate portion.