PURPOSE: To surely estimate the liquid amount in a liquid can by providing a plurality of guide parts standing on float sides and exposing to a can opening and a scale plate arranged in the float approximately in parallel to the guide parts.

CONSTITUTION: The fixing parts 2a for guide parts 2 are jointed to each recess on a float 1 to fix the guides 2. A scale plate 3 is inserted from the bottom of the float 1 penetration hole, a fixing pin is inserted one of appropriate positioning holes and the scale plate 3 is fixed with a weight 8 to the float 1. The float 1 is inserted from the opening 11 of an empty liquid can 10 until the weight touches the bottom of the can 10. The float 1 in this state is arranged just below the opening 11. When an injection pipe is inserted in the opening 11 to inject liquid, the liquid amount increases, the float 1 is risen by the buoyancy and the guides 2 touch and slide on the inner wall of the opening 11. During this rise, the scale 3 is read to the reference top 11a of the opening 11 and then, the present liquid amount in the can 10 is visually confirmed.