Disclosed is a heat treatment apparatus (100) which comprises: a treatment chamber (1) in which a wafer (W) is contained; a substrate supporting unit (4) for horizontally supporting the wafer (W) within the treatment chamber (1); and a lamp unit (3) that is provided above the treatment chamber (1). The lamp unit (3) comprises: a base member (40); a plurality of lamps (45) that are provided on the lower surface of the base member (40) with the front ends facing down; a plurality of ring-shaped reflectors (41, 42, 43) that are concentrically provided on the lower surface of the base member (40) so as to project downward; and a cooling head (47) for supplying a cooling medium into the reflectors (41, 42, 43). At least some of the plurality of lamps (45) are arranged along the reflectors (41, 42, 43), and cooling medium channels (68), each of which is composed of a ring-shaped space, are provided within the reflectors (41, 42, 43) in the arrangement direction of the reflectors.