An occupant weight detecting apparatus for detecting an occupant weight on a seat includes a load sensor mounted on the seat to detect a load on the seat and output a load signal. A detected load value is calculated periodically based on the load signal and an average is calculated based on the detected load values calculated during a period in which the detected load value is less than a first predetermined. The average of the detected load values is set to a zero point, and the occupant weight is detected based on the detected load value and the zero point when the detected load value exceeds a second predetermined value.