The invention concerns an injection device comprising a syringe body tubular element (9) provided with finger-pressing members (23) for holding said injection device to inject a dose of liquid, in particular medicinal liquid. The invention is characterised in that the finger-pressing members consist of a flange (23), provided with an upper surface and a lower surface, including two portions with symmetrical outline (50, 51), called gripping portions, having lower support surfaces for the user's fingers, and between said support surfaces, two portions with diametrically opposed symmetrical outlines (52), called indexing portions, including in the extension of the lower surface of said flange, a lower surface having a convex profile formed by two slopes symmetrical relative to a longitudinal axis.