A cylinder head for an internal combustion engine in which any of a plurality of valve guides for guiding intake and exhaust poppet valves provided with valve lifters can be press-fitted in fitting holes of the cylinder head with a substantially uniform press fit force. At least one valve guide is fitted at a different depth in the cylinder head than others of the guides valves. The intake and exhaust poppet valves have substantially uniform thicknesses in the respective longitudinal directions of the valve guides. An idle fitting hole with an inner diameter greater than an outer diameter of the valve guides is formed above one of the fitting holes which is formed deeper in the cylinder head than the other fitting holes, the idle fitting hole extending upward to a lower side of a valve spring.