An occupant-classifying system includes a load-detecting device assembled at a vehicle seat for detecting a load value imposed on the vehicle seat and for outputting the load value, and a controller for determining whether the vehicle seat is in an occupied state, or in an unoccupied state on a basis of the load value outputted from the load-detecting device. A seat occupied state is classified into plural modes defined on a basis of plural threshold load values. The controller is configured to determine the seat occupied state when the load value falls within a specific mode among the plural modes and lasts for a predetermined time duration defined for each specific mode. The controller changes one of the threshold load values which define a boundary between the selected mode and another, neighboring mode, whether occupied mode or unoccupied mode.