A constant current device and a heat dispersion module thereof used for stabilizing a current of a light emitting unit are disclosed. The heat dispersion module includes an impedance element, a detection control unit, a switch unit, and a feedback unit. The detection control unit is used to detect a node voltage value between the light emitting unit and a current regulating unit. The switch unit switches between an on-state and an open state; when the switch unit is in the on-state, a current of the current regulating unit is conducted to a ground via the switch unit; when the switch unit is in the open state, the current of the current regulating unit is conducted to the ground via the impedance element. The feedback unit causes the switching unit to exhibit hysteresis when changing between the on-state and the open state.