Seatbelt system for vehicle, and control method for seatbelt system

A seatbelt system includes a take-up device configured to take up a seatbelt, and an electronic control unit configured to, when any one of first and second conditions is satisfied, cause a motor to take up the seatbelt. In the first condition, after occurrence of a collision whose physical quantity detected by a detector configured to detect the physical quantity associated with a magnitude of the collision is less than or equal to a first threshold, the physical quantity decreases to less than or equal to a second threshold. In the second condition, after occurrence of a collision whose physical quantity is less than or equal to the first threshold, a first predetermined time elapses, which is estimated to be equivalent to a decrease in the physical quantity to less than or equal to the second threshold.