A power reserve mechanism (100), simple in mechanism without any planetary gear mechanism, comprising a first winding stem train wheel (150) in charge of the winding stem of a ratchet wheel (2) and a second winding stem train wheel (160) in charge of the winding stem of a complete barrel which are disposed separately from each other, wherein a first indicator (51) is disposed on the first winding stem wheel (5) of the first winding stem train wheel (150), and a second indicator (81) is disposed on the second winding stem wheel (8) of the second winding stem train wheel (160), both of the first and second indicators (51 and 81) being rotated in the same direction. The amount of reserved spring power is displayed utilizing a relative variation in movements of these indicators.