PROBLEM TO BE SOLVED: To discharge remaining air from an inside sealed space to the outside with a simple structure when injecting paste into the inside of a cylinder.SOLUTION: An ejector for paste has an annular concave groove 9 formed in an outer periphery near the front end of a plunger member 4 and an O-ring 10 for blocking the flow of air to an ejecting port 11 side and a rear end opening part side, a groove width from a front face 9a to a rear face 9c spaced apart in fore and aft directions in a bottom face 9b of the annular groove 9 is formed greater than the thickness of the O-ring 10. An air releasing groove 14 is formed in the fore and aft directions in the bottom face of the annular groove 9. The air releasing groove 14 allows air to flow but the paste can not pass through the air releasing groove 14 because the flowing resistance is great with respect to the paste.
