A vacuum laser constant temperature device is adopted for a housing that has a heat dissipation module arranged therein. The device has a metallic partition adjacent to the heat dissipation module to enclose a airtight vacancy formed with the housing, a thermoelectric cooling chip with a heating portion connecting to a side of the metallic partition and a cooling portion, a semiconductor laser lighting module arranged in the airtight vacancy and connecting to the cooling portion of the thermoelectric cooling chip, and a heat insulation layer arranged both on an opposite side of the metallic partition and in the airtight vacancy. Heat generated by the semiconductor laser lighting module can be transferred to the heat dissipation module via the thermoelectric cooling chip and the metallic partition. The thermoelectric cooling chip makes an output power of the semiconductor laser lighting module keep constant within various environments without the condensation thereon.