To provide an engine auxiliary machine attaching structure capable of using the same cylinder head and promoting the use of common part items even if the number of auxiliary machines and kinds thereof disposed in the vicinity of the rear end part of an engine are different.

In an engine 1, if both a vacuum pump 51 and a power steering oil pump 52 are provided in the vicinity of the rear end part of the engine, a gear case 50 is attached to a counter lock section 53 formed in the rear end part of the cylinder head, and the vacuum pump 51 is attached to the socket section of the gear case 50. On the other hand, if only the vacuum pump 51 is provided in the vicinity of the rear end part of the engine, the vacuum pump is directly attached to the counter lock section 53. Thus, even if the number of auxiliary machines and kinds thereof disposed in the vicinity of the rear end part of the engine are different, the same cylinder head is used and the use of common part items is promoted.