An occupant detection method includes detecting a load applied to a seat for a vehicle, detecting that an occupant is seated at the seat, holding a local maximum of the load which is detected when the occupant becomes seated, setting a standard value of the load in a state in which the occupant is seated at the seat, and estimating a body height of the occupant on the basis of a comparison between the local maximum of the load and the standard value of the load, wherein when the body height of the occupant is estimated, the larger a difference between the local maximum of the load and the standard value of the load is, the higher body height of the occupant is estimated.