Provided are a syringe plunger, a method of manufacturing the same, and a medical syringe, with which a degree of welding at a contacting surface of a gasket and a plunger body is uniform, and with which it is possible to prevent the gasket becoming detached from the plunger body, and to prevent the occurrence of shape deformation resulting from positional displacement and strain of the gasket when the plunger body is being mounted onto the gasket. According to the present invention, a syringe plunger 21 is provided with a plunger body 20, a connecting portion 24 provided at a distal end of the plunger body 20, and a gasket 23 a distal end of which is closed and a rear end of which is open, and which accommodates at least a portion of the connecting portion 24 from the rear end side. A recessed portion 27 is provided in a central portion of a distal end surface of the connecting portion 24. The recessed portion 27 is a molten resin receiving portion for receiving molten resin for gasket molding that is supplied when the gasket 23 is being molded, and an inner wall surface of the gasket 23 is welded to the connecting portion 24 at a contacting surface including at least the recessed portion 27.Linvention porte sur un piston de seringue, son procédé de fabrication, et sur une seringue médicale, avec lesquels le degré de soudure, au niveau du point de contact entre le joint détanchéité et le corps du piston, est uniforme, et avec lequel il est possible dempêcher le joint détanchéité de se détacher du corps du piston, et dempêcher sa déformation causée par le déplacement et la contrainte sur le joint détanchéité lorsque le corps du piston est monté sur le joint détanchéité. Selon la présente invention, un piston de seringue 21 est pourvu dun corps de piston 20, dune partie de liaison 24, située au niveau de lextrémité distale du corps de piston 20, et dun joint détanchéité 23, dont lextrémité distale est fermée et dont lextrémité postérieure est ouverte, qui reçoit, au
