A seat with an alertness-maintaining device that can efficiently secure a drive source (for example, a motor) when the drive source is internally housed and a vibratory stimulus is imparted to the occupant. The present disclosure relates to a seat with an alertness-maintaining device, the seat being provided with an alertness-maintaining device for imparting physical force to the occupant to promote alertness. A load-supporting portion for supporting the load on the back of the occupant is installed, and a device drive unit for imparting physical force to the occupant, the device drive unit that forms the alertness-maintaining device, is attached to the load-supporting portion. The device drive unit is provided with a drive source and a support member. The support member is attached to the load-supporting portion while grasping a part of the load-supporting portion by a drive source attachment surface portion and a load-supporting portion-clamping piece.