This invention relates to an ampoule opening device (1) for the opening of glass ampoules (100) of the type used in particular in the pharmaceutical field for injection substances. The device according to this invention allows opening, by rupture of the neck of the ampoule, glass ampoules of different capacities (and therefore of sizes), by generating a non irregular rupture edge and therefore minimizing the creation of glass fragments that may fall into the substance contained within the ampoule. Moreover, the device object of this invention allows avoiding contact of the user's fingers with the neck and the cap of the ampoule, thereby preventing any risk of accidental injuries. The device object of this invention allows obtaining excellent results in terms of quality of the rupture edge of the ampoule neck and of repeating the result obtained thanks to the fact that the device allows to apply to the ampoule a constant rupture bending moment for ampoules of the same type.