the present invention relates to a device for reversibly supporting the seat of a vehicle . when a tractor or like vehicle is used for working with a backhoe or like work machine attached to the rear end of the vehicle , a forward operation seat and a rearward operation seat are conventionally needed and are therefore uneconomical . furthermore , the work mahcine must be spaced from the vehicle body to avoid interference between the two sheets . this entails the problem of impairing the weight balance longitudinally of the vehicle . to overcome these problems , a support table is mounted on the vehicle body by a parallel link assembly which is pivotally movable longitudinally of the body , and a swivel table for supporting the seat thereon is mounted on the support table swivelably about a vertical shaft . further provided is a lock for locking the swivel table against swiveling about the shaft , and unlocking device for unfastening the lock . the swivel table is unlocked by the unlocking device when the link assembly is raised to an upright position . the single seat is then swiveled about the shaft for forward operation and also rearward operation . the seat is locked against swiveling by the lock . when the link assembly is brought to the upright position , the seat can be unlocked by the unlocking device .