A lamp device has a base body to be installed to a vehicle; a lamp unit; a translucent cover that is installed to the base body, covering the front surface of the base body so as to accommodate the lamp unit therein, thereby defining a lamp body space, and has a recess in the front surface at a side position in a horizontal direction of the lamp unit; and a radar unit that has a radar sensor and a radar housing accommodating the radar sensor therein, and is inserted in the recess.