An oil level gauge guide apparatus including a body of an internal combustion engine, a case member attached to the body so as to cover a moving part disposed on a side of the body, a passage forming member forming a gauge passage through which an oil level gauge passes between the body and the case member, and a guide portion provided at a lower part of the passage forming member to guide the oil level gauge to the gauge passage. The body and the case member include a first and second facing surfaces facing each other so as to form a space to accommodate the moving part and the guide portion is extended along the gauge passage and protruded from one of the first facing surface and the second facing surface to the other of the first facing surface and the second facing surface.