To provide an instrument and a method for measuring a muzzle velocity capable of avoiding a disadvantage in measurement by one existing coil device or two existing coil devices.

This device 10 and method are used for determining the muzzle velocity Vo of a projectile 1 in outgoing from a gun barrel. The device 10 includes a coil 12 positioned around a longitudinal shaft 11.1 of the gun barrel 11 in an area before the outgoing, and an electric power source 15 for impressing a current to the coil to generate a magnetic field H. The device 10 includes additionally an analyzer 16 for reading out a voltage pulse induced during a period when the projectile 1 on the coil 12 is passed through the magnetic field of the coil 12. Two predetermined points of the voltage pulse are detected, a time interval between the two points is determined, and the the muzzle velocity Vo of the projectile 1 is calculated based on the time interval.