A compressor includes a casing and a motor disposed inside the casing. The motor is welded to the casing at a plurality of weld positions. The motor includes a core, a coil, at least one insulating member, recesses and a gap. The core has an annular back yoke portion, a plurality of tooth portions projecting radially inwardly from the back yoke portion and a slot formed between the tooth portions adjacent to each other. The coil is disposed in the slot. The insulating member is disposed in the slot to insulate the coil from the core. The recesses are formed in portions of the back yoke portion with each recess facing the slot. The gap is provided between the back yoke portion and the insulating member.