A bed apparatus includes: a mattress mounted on a bed body and, first cells arranged on both left and right sides in a longitudinal direction of the bed body. The bed apparatus is configured to change the body position of a patient on the mattress by inflating the first cells alternately. In the apparatus, the first cells on the left and right sides are inflated, and when a difference in pressure between the first cells on the left and right sides has continuously fallen within a decision pressure value range for a decision pressure value continuation time, the body position of the patient is changed, whereas when the difference in the pressure between the first cells on the left and right sides has not continuously fallen within the decision pressure value range for the decision pressure value continuation time or when the difference in the pressure between the first cells on the left and right sides has continuously fallen out of the decision pressure value range for the decision pressure value continuation time, change of the body position of the patient will not be performed. With this, it is possible to provide a bed apparatus and the like that can detect the place of the patient lying on the bed before changing the body position of the patient to thereby prevent the patient from falling from the bed apparatus.
