A microwave device includes: a first multilayer resin substrate including a ground via hole; a semiconductor substrate provided at the first multilayer resin substrate and including a high frequency circuit; and a conductive heat spreader provided at an opposite face of the semiconductor substrate from a face of the semiconductor substrate facing the first multilayer resin substrate. The microwave device includes: a resin provided over the first multilayer resin substrate and covering the semiconductor substrate and the heat spreader such that an opposite face of the heat spreader from a face of the heat spreader facing the semiconductor substrate is exposed as an exposed face; and a conductive film covering the resin and the heat spreader and touching the exposed face. The semiconductor substrate includes a ground through hole extending through the semiconductor substrate. The conductive film is electrically connected to the ground via hole via the heat spreader and the ground through hole.