An injection molding apparatus includes a melting section configured to melt a solid material into a shaping material and a nozzle configured to inject the shaping material supplied from the melting section into a mold. The melting section includes a screw having a groove forming surface on which a groove is formed, a barrel having an opposed surface opposed to the groove forming surface, a communication hole communicating with the nozzle being provided in the barrel, a heating section configured to heat the solid material supplied to between the screw and the barrel, a driving motor, a first gear configured to transmit a driving force of the driving motor to the screw and rotate the screw, and a first injecting section including a first injection port for injecting a first lubricant and a first injection path leading from the first injection port to the first gear.