A process for producing unsaturated nitrile, using a fluidized bed reactor and comprising a reaction step of subjecting hydrocarbon to a vapor phase catalytic ammoxidation reaction in the presence of a catalyst to produce the corresponding unsaturated nitrile, wherein when an internal space of the reactor is divided into two spaces of an upper space occupying a space from an upper end of an inlet of a cyclone to an upper end of the internal space and a lower space occupying a space below the upper end of the inlet of the cyclone and ranging to a dispersion plate, a ratio of an existing amount of the catalyst in the upper space to an existing amount of the catalyst in the lower space is 0.05 to 0.45 in the reaction step.