To provide a bed occupancy state detection method capable of determining a bed user's movement of raising the back on a bed by following his/her speed of raising.

The detection method includes: a load detection step of detecting loads applied to a head-side right part, a head-side left part, a leg-side right part, and a leg-side left part of a bed part 21 respectively by first to fourth load detection sensors 1A-1D; an output value data storage step S5 of calculating and storing a head-side output value H obtained by totalizing output values W1 and W2 from the first and second load detection sensors 1A and 1B; a back-raising determination step S7 of determining whether or not at least one of prescribed first condition and second condition relating to a diminution rate of the head-side output value H is satisfied; and a notification step S28 of notifying of information that, when it is determined that at least one of the first condition and the second condition is satisfied, a bed user U on the bed 21 performs the back-raising movement.