An occupant determination apparatus and an occupant determination method are provided that can accurately determine the size of an occupant, with a simple configuration where a plurality of electrodes are arranged on one layer, and can eliminate errors due to the capacitance between an occupant and surrounding car-body metal parts or the like, and thus suppress erroneous determination. The occupant determination apparatus (10) comprises a first sensor (11) including a plurality of seat section electrodes (111 to 117) arranged on a sitting section (1a), and a first determination section (20). The first sensor section (11) comprises: a first seat section electrode (111); a reference electrode array (12a) where second seat section electrodes (112 to 114) are arranged separate in the x-direction; and a reference electrode array (12b) where third seat section electrodes (115 to 117) are arranged separate in the x-direction, arranged separate in the y-direction. The first determination section (20) comprises: an oscillator (22); a capacitance detecting section (23) which detects the current flowing through a seat section electrode in order to detect the capacitance; a switching circuit (21) which switches the connection of the capacitance detecting section (23) to the seat section electrode; and a controlling section (26) which outputs a switch control signal.