The utility model discloses install on an indoor exercise bicycle, this indoor exercise bicycle has a frame and a flywheel, and this flywheel is equipped with a magnetism portion, the utility model discloses contain a link, two magnetite seats and several magnetic component, this link is installed on this frame, two magnetite seats are located the both sides of this flywheel respectively, the several magnetic component install respectively in the two magnetite seats to correspond the magnetism portion that attracts this flywheel, during the in -service use, will two magnetite seats are established in the both sides of this flywheel, through several magnetic component's magnetic force attracts to cause the resistance to this flywheel, because magnetic force is non -contact external force, so the utility model discloses wearing and tearing in the time of avoiding receiving the flywheel and rotate and cause and destroy, in addition two magnetite seats are two independent components, and are comparatively easy in the mould development, therefore can save the cost of manufacture.