An injection molding machine includes: a timing belt wound around a driving-side rotation member and a driven-side rotation member and configured to transmit power from the driving-side rotation member to the driven-side rotation member; a driving-side rotation detecting unit configured to detect a rotational speed of the driving-side rotation member; a driven-side rotation detecting unit configured to detect a rotational speed of the driven-side rotation member; and an abnormality detecting unit configured to detect an abnormality in the timing belt based on a relative speed difference between the rotational speed of the driving-side rotation member detected by the driving-side rotation detecting unit and the rotational speed of the driven-side rotation member detected by the driven-side rotation detecting unit in a predetermined period after the driving-side rotation member starts to rotate from a stopped state.