Abstract: A position estimation method capable of quickly estimating a position of an end of a cylindrical object. A holding-robot controller includes a correction control amount computation part configured to output a correction control amount of a position and a posture of a holding tool so as to reduce the chuck width. The position estimation method includes: a step of causing a pair of clamping claws to approach each other in a reference position and a reference posture to temporarily hold an engine damper; a step of correcting the position and the posture of the holding tool using a correction control amount; a step of causing the pair of clamping claws to approach each other in the position and the posture after the position/posture correction step to temporarily re-hold the engine damper; and an end position estimation step of estimating end position coordinates of the engine damper.