The invention relates to a needleless injection device (10) having a body (12) forming a receptacle (44) which is delimited by a tubular wall (46) and which extends axially from an upper radial seat (48), a gas generator (16), a tubular reservoir (24) which encloses an active principle (26) and which extends axially in said receptacle (44) from an upper end forming an upper flange (40) to a lower end (36), an elastically deformable membrane (50) in the general shape of a T, which comprises a radial annular disc (52) that is interposed axially between the upper flange (40) of the reservoir (24) and said seat (48), and a tubular part (54) which extends axially in the reservoir (24), characterized in that it has an annular washer (64) which is interposed axially between the annular disc (52) of the membrane (50) and the upper flange (40) of the reservoir (24).
