Abstract: A lubrication apparatus for an engine includes a crankshaft chamber, a camshaft chamber, and an oil reservoir chamber, wherein an oil-suction piping path is provided in the oil reservoir chamber, and is communicated between the crankshaft chamber and the oil reservoir chamber. The oil-suction piping path includes, among others, a rotatable pipe including a plurality of oil-suction orifices located at wall of the rotatable pipe. No matter the engine is situated at any state of declination, at least one of the oil-suction orifices and an air-suction vent is kept under the surface of the lubricant, so that the engine can be appropriately lubricated. Further, a one-way valve is arranged between the crankshaft chamber and the oil reservoir chamber, where most of the lubricant can flow back to the oil reservoir chamber during the descending stroke of a piston, so that a lubricant supply can be reduced.