A transmission comprising: a first rotating shaft as a drive shaft that is driven by an engine source; a second rotating shaft as a driven shaft that is driven by the drive shaft and is arranged parallel to the first rotating shaft; a first gear attached to the first rotating shaft so as to be unrotatable and axially unmovable relative to the first rotating shaft; a second gear that is attached to the second rotating shaft so as to be rotatable and axially unmovable relative to the second rotating shaft and is in mesh with the first gear; and a slide ring that is attached to the second rotating shaft so as to be unrotatable and axially movable relative to the second rotating shaft and is adjacent to the second gear in an axial direction, wherein: the slide ring includes an annular portion that is concentric with the second rotating shaft, and a plurality of protruding portions that extend radially inward from the annular portion and are arranged next to each other in a circumferential direction; the second gear includes dogs that protrude in the axial direction; the slide ring includes engagement holes, defined by the annular portion and the protruding portions, into which the dogs are inserted; the transmission being characterised in that distal end portions of the protruding portions of the slide ring are not linked together; the first gear and the second gear are helical gears each including a plurality of teeth inclined relative to the axial direction, and are configured so that the second gear receives, from the first gear, a thrust force in a direction toward the slide ring. a first rotating shaft as a drive shaft that is driven by an engine source; a second rotating shaft as a driven shaft that is driven by the drive shaft and is arranged parallel to the first rotating shaft; a first gear attached to the first rotating shaft so as to be unrotatable and axially unmovable relative to the first rotating shaft; a second gear that is attached to the second rotating shaft so as to be rotatable and axially unmovable relative to the second rotating shaft and is in mesh with the first gear; and a slide ring that is attached to the second rotating shaft so as to be unrotatable and axially movable relative to the second rotating shaft and is adjacent to the second gear in an axial direction, wherein: the slide ring includes an annular portion that is concentric with the second rotating shaft, and a plurality of protruding portions that extend radially inward from the annular portion and are arranged next to each other in a circumferential direction; the second gear includes dogs that protrude in the axial direction; the slide ring includes engagement holes, defined by the annular portion and the protruding portions, into which the dogs are inserted; the transmission being characterised in that distal end portions of the protruding portions of the slide ring are not linked together; the first gear and the second gear are helical gears each including a plurality of teeth inclined relative to the axial direction, and are configured so that the second gear receives, from the first gear, a thrust force in a direction toward the slide ring. the slide ring includes an annular portion that is concentric with the second rotating shaft, and a plurality of protruding portions that extend radially inward from the annular portion and are arranged next to each other in a circumferential direction; the second gear includes dogs that protrude in the axial direction; the slide ring includes engagement holes, defined by the annular portion and the protruding portions, into which the dogs are inserted; the transmission being characterised in that distal end portions of the protruding portions of the slide ring are not linked together; the first gear and the second gear are helical gears each including a plurality of teeth inclined relative to the axial direction, and are configured so that the second gear receives, from the first gear, a thrust force in a direction toward the slide ring.