A lubricating apparatus for an internal combustion engine is provided in which an oil discharge passage, extending from the oil pump, is provided for straddling the oil pump case and the tank body. A direction of the extension of the oil discharge passage is changed in the tank body such that the oil discharge passage further extends in parallel with a junction plane between the oil pump case and the tank body. An opening for pressure reception by a relief valve is provided in the oil discharge passage portion extending in parallel with the junction plane. By attaching the oil pump case such that an outside end portion of the relief valve is held by a portion of the oil pump case, the relief valve is fixed between the tank body and the oil pump case.