A seat system for a vehicle, includes a first pair of slide rails and a second pair of slide rails arranged on a vehicle compartment floor so as to extend in a front-rear direction of the vehicle, a first seat and a second seat arranged alongside each other, a forward-rearward movement mechanism provided under each of the first and second seats and supported at each of the first and second pairs of slide rails so that each of the first and second seats is movable along each of the first and second pairs of slide rails, and a sway mechanism provided between each of the first and second seats and the forward-rearward movement mechanism and swayably supporting each of the first and second seats at least in a direction where each of the first and second seats is approaching another of the first and the second seats.