In order to inhibit overshoot in the concentration of a source gas immediately after a gas supply period starts, there is provided a vaporization device that is equipped with a vaporization tank that holds a liquid or a solid source, a carrier gas supply path that supplies carrier gas to the vaporization tank, a source gas extraction path along which flows a source gas which is obtained by vaporizing the source and which is extracted from the vaporization tank, a concentration monitor that is provided on the source gas extraction path, and a concentration control mechanism that is provided with a fluid controller which controls a concentration of the source gas extracted from the source gas extraction path. This vaporization device alternates between supplying the source gas and stopping the supply of the source gas.