1. A work robot system comprising:a conveying apparatus that conveys an object;
a robot that performs a predetermined task on a target portion of the object being conveyed by the conveying apparatus;
a controller that controls the robot;
a movement amount detector that detects a movement amount of the object moved by the conveying apparatus; and
a force detector that detects a force generated by contact between a part or a tool supported by the robot and the object, wherein
when the predetermined task is performed by the robot, the controller performs force control based on a value detected by the force detector while performing control of the robot by using information about a position of the target portion and a value detected by the movement amount detector; and
the controller is configured to shorten a control cycle of force control or enhance sensitivity of the force control when the value detected by the movement amount detector varies to exceed a predetermined reference.