To provide a monoblock engine capable of improving manufacturability of an engine, by reducing the number of parts.

A camshaft driving mechanism includes: an intermediate shaft 29 orthogonal to the axis of a crankshaft 7 and the axis of a camshaft 6; a first bevel gear 32 synchronously rotating with the crankshaft 7; a second bevel gear 33 arranged in a lower end part of the intermediate shaft 29 and meshing with the first bevel gear 32; a third bevel gear 34 arranged in an upper end part of the intermediate shaft 29; and a forth bevel gear 35 for synchronously rotating with the camshaft 6 and meshing with the third bevel gear 34. A storage part 31 for storing the intermediate shaft 29 and a bearing 19 for supporting the intermediate shaft 29 is integrally formed with an engine block main part 1. An oil pump 39 can also be integrated with the engine block main part 1 by arranging the oil pump 39 driven by the intermediate shaft 29 in the storage part 31.