ENGINE

The present invention provides an engine that can optimize valves and their advancing/retreating mechanisms in the vicinity of a cylinder chamber. The engine 10 comprises: a cylinder chamber 12, an intake valve 18, an exhaust valve 19, and an advancing/retreating mechanism 20 that advances and retreats the intake valve 18 and the exhaust valve 19. The advancing/retreating mechanism 20 has a camshaft 21, an exhaust cam 22, an intake cam 23, a pushrod 24, and a rocker arm 25. The intake cam 23 is fixed to the camshaft 21 and is configured to advance and retreat the intake valve 18. The exhaust cam 22 is configured to advance and retreat the pushrod 24. The rocker arm 25 is rotated by the pushrod 24 and is configured to advance and retreat the exhaust valve 19.