An occupant classifying device for a vehicle seat includes an occupant classifying apparatus for classifying an occupant type on the basis of a seating load applied to the vehicle seat, a first load sensor provided at a rear portion of the vehicle seat in order to measure a rear load that is a part of the seating load, a second load sensor provided at a front portion of the vehicle seat in order to measure a front load that is a part of the seating load, a rear load ratio calculating apparatus for calculating a rear load ratio indicating a ratio of the rear load in the seating load on the basis of the measured rear and front loads and a securing determining apparatus determining whether or not a child restraint system is secured to the vehicle seat on the basis of the calculated rear load ratio.