A machining apparatus, comprising: a cover including a side plate, a projecting portion connected to the side plate, the projecting portion disposed below the side plate, a front opening having a rectangular shape located on the side plate, and a planar opening having a semicircular shape located above the projecting portion, the planar opening connected to the front opening; a first door body (29, 129) including a first drum disposed in a first side with respect to a mating surface, a first abutting surface connected to the first drum, and a first top plate connected to the first drum and the first abutting surface, the first door body (29, 129) configured to be accommodated inside the cover by rotating about a first axis that is offset toward a second side with respect to the mating surface; and a second door body (34, 134) including a second drum disposed in the second side with respect to the mating surface, a second abutting surface connected to the second drum, the second abutting surface configured to abut to the first abutting surface on the mating surface, and a second top plate connected to the second drum and the second abutting surface, the second door body (34, 134) configured to be accommodated inside the cover by rotating about a second axis that is offset toward the first side with respect to the mating surface. a cover including a side plate, a projecting portion connected to the side plate, the projecting portion disposed below the side plate, a front opening having a rectangular shape located on the side plate, and a planar opening having a semicircular shape located above the projecting portion, the planar opening connected to the front opening; a side plate, a projecting portion connected to the side plate, the projecting portion disposed below the side plate, a front opening having a rectangular shape located on the side plate, and a planar opening having a semicircular shape located above the projecting portion, the planar opening connected to the front opening; a first door body (29, 129) including a first drum disposed in a first side with respect to a mating surface, a first abutting surface connected to the first drum, and a first top plate connected to the first drum and the first abutting surface, a first drum disposed in a first side with respect to a mating surface, a first abutting surface connected to the first drum, and a first top plate connected to the first drum and the first abutting surface, the first door body (29, 129) configured to be accommodated inside the cover by rotating about a first axis that is offset toward a second side with respect to the mating surface; and a second door body (34, 134) including a second drum disposed in the second side with respect to the mating surface, a second abutting surface connected to the second drum, the second abutting surface configured to abut to the first abutting surface on the mating surface, and a second top plate connected to the second drum and the second abutting surface, a second drum disposed in the second side with respect to the mating surface, a second abutting surface connected to the second drum, the second abutting surface configured to abut to the first abutting surface on the mating surface, and a second top plate connected to the second drum and the second abutting surface, the second door body (34, 134) configured to be accommodated inside the cover by rotating about a second axis that is offset toward the first side with respect to the mating surface.