Seat device for a vehicle and vehicle provided therewith

In a seat device for a vehicle comprising a front-row seat including a driver seat 7a and an assistant seat 7b and a rear-row seat 8b provided behind the front-row seat, respective front-row and rear-row seats being provided in a cabin 2 which includes an ingress and egress opening 1a, 1b at a side face, the rear-row seat 8b is configured so as to be located in a normal use position and in a stored position SP where a longitudinal thickness thereof is made short, and the assistant seat 7b is configured so as to be moved rearward from a position beside the driver seat 7a to a position which corresponds to the normal use position of the rear-row seat 8b.Accordingly, a space in the cabin properly can be utilized, by effectively enlarging a rearward-movement range of the front-row seat including the assistant seat with a simple structure.