A human-interactive type robot system which can constantly detect a contact force at a high precision even if the contact force is small, comprising a force sensor which measures a force which the robot receives from the outside and outputs a measurement value, a force detection value calculating part which subtracts a correction value from the measurement value to calculate a force detection value, and a correction value updating part which updates a force detection value when a predetermined condition stands for use as the correction value. The predetermined condition is that the robot is stopped or operating at a fixed speed and a margin of fluctuation of the force detection value at a predetermined unit time is a fluctuation margin threshold value or less or that the robot is stopped and the current force detection value is the force detection value threshold value or less.