Abstract: In a valve-operating device with a breather system in an engine, in which a breather passage is defined in a cam shaft, a bearing cap is detachably secured to the engine body for supporting an outer peripheral surface of one end portion of the camshaft with a bearing. A breather chamber is provided in the bearing cap in order to communicate with the outlet of the breather passage. A pipe-connecting portion is integrally formed on an outer peripheral surface of the bearing cap; and a breather pipe connected to an intake system is connected to the pipe-connecting portion. Thus, a blow-by gas can be drawn through the breather passage in the valve-operating camshaft to the outside by utilizing a portion of a valve-operating camshaft supporting structure. It is thus possible to simplify the structure of the valve-operating device with the breather system.