PROBLEM TO BE SOLVED: To reduce push-in force of a plunger.SOLUTION: A dental paste extractor includes a plunger 3 including an annular recessed groove 14 formed for mounting an O-ring 15 as a seal material. The O-ring 15 includes a reinforcement part 15c extending forward from a front side of the O-ring 15, and coming into contact with an inner peripheral surface of the annular recessed groove 14, formed with it non-contact with the inner peripheral surface of a cylinder 2.SELECTED DRAWING: Figure 5COPYRIGHT: (C)2016,JPO&INPIT