An injection molding machine includes supporting plates, molds coupled to the supporting plates, and a coupling guide device to guide the coupling of the molds and the supporting plates. The coupling guide device includes a first coupling guide recess and a first coupling guide protrusion provided at center portions of the molds and the supporting plates so as to be coupled to each other, and a second coupling guide recess and a second coupling guide protrusion provided at the molds and the supporting plates, spaced apart from the first coupling guide recess and the first coupling guide protrusion, so as to be coupled to each other. The second coupling guide recess is formed lengthwise in a direction toward a periphery from the center portions of the molds and the supporting plates.