Abstract: According to one embodiment, a substrate treatment apparatus includes a substrate holding unit including a holding unit configured to hold a target substrate, a base unit which has the holding unit on a peripheral portion thereof, and a hollow rotation shaft, which contains a gas supply channel, configured to rotate together with the holding unit and the base unit, the substrate holding unit configured to hold the target substrate by supplying to the target substrate gas supplied from the gas supply channel, a substrate rotating unit, which is connected to the rotation shaft through a belt, configured to rotate the substrate holding unit, and a first substrate holding detecting unit, which is connected to the substrate rotating unit, configured to detect whether or not the target substrate is held by the substrate holding unit, by measuring a rotational frequency or a roll acceleration of the rotating substrate holding unit.