A compliant mechanism includes a first unit, a second unit, at least one elastic member and a driver for driving the elastic member to rotate through a predetermined angle. The first and second units collectively define a passage about which the second unit is rotatable relative to the first unit. The elastic member has a plate and first and second shafts which are coaxially connected to two opposite ends of the plate respectively and rotatably connected with the first and second units respectively. The elastic member is rotatable about a co-axis of the first and second shafts and elastically deformable when the second unit rotates relative to the first unit. The elastic member can change its resistance to the rotation of the second unit by rotating; therefore the compliant mechanism has a great safety upon receiving load and is widely applicable in many fields.