An automatic circle forming apparatus adapted for automatically forming OPP (O-phenylphenol) plastic circles includes a lower equipment cabinet, a first base plate, a transmitting module, an automatic separating module, an automatic tearing film module, a sucking waste mechanism, a displacement module, an automatic forming module and an upper equipment cabinet. The upper equipment cabinet is positioned on the first base plate for installing the transmitting module, the automatic separating module, the automatic tearing film module, the sucking waste mechanism, the displacement module and the automatic forming module therein. The upper equipment cabinet is equipped with a man-machine control interface which connects with and controls the transmitting module, the automatic separating module, the automatic tearing film module, the sucking waste mechanism, the displacement module and the automatic forming module for automatically forming the OPP plastic circles so as to improve operation efficiency and save a human cost.