Seating state detection device

A seating state detection device comprising:

• an acquisition unit configured to acquire a detection signal group in a predetermined period that is output as a result of transmission and reception of waves by a radio wave sensor mounted on a vehicle;
• a signal extraction unit configured to extract specific-intensity signals in a predetermined reflection intensity range from the detection signal group, and
• a determination unit configured to determine whether an occupant in the vehicle is in a first riding state in which the occupant is directly seated on a seat or in a second riding state in which the occupant is seated in an infant auxiliary device, based on a distribution mode of the specific-intensity signals,
• wherein the determination unit determines whether the occupant is in the first riding state or the second riding state, based on a distribution position of a number of specific-intensity signals, and
• wherein the distribution position of the number of specific-intensity signals indicates one of a first distribution region for the first riding state or a second distribution region for the second riding state.