A laser apparatus includes: a cooling capacity control means which controls the cooling capacity of a heat receiving/cooling unit; a surrounding member which surrounds a dew condensation prevention target unit including a heat generating unit and which reaches a surrounding member equilibrium temperature higher than the maximum dew point temperature within a housing as the temperature of the heat generating unit is increased; and a temperature detection means which detects the temperature of the surrounding member, a control unit compares, while a current output command is being output to a laser power supply unit, a surrounding member temperature with a switching temperature previously set lower than the surrounding member equilibrium temperature and when the surrounding member temperature is lower than the switching temperature, the control unit controls the cooling capacity control means such that the cooling capacity of the heat receiving/cooling unit is a low level whereas when the surrounding member temperature is equal to or more than the switching temperature, the control unit controls the cooling capacity control means such that the cooling capacity of the heat receiving/cooling unit is equal to or higher than a standard level.