A voice operation system includes: an image forming apparatus that forms an image on a recording material; a server that accepts voice information related to an operation on the image forming apparatus, and gives an operation instruction to the image forming apparatus; and a voice input/output device that converts an input voice into voice information, sends the voice information to the server, receives voice information as a response to the voice information related to the operation on the image forming apparatus, and emits a sound of the voice information, wherein the server has a hardware processor that stores information on a part of a function or configuration of the image forming apparatus, and the server determines executability of an operation associated with voice information transmitted from the voice input/output device, and causes the image forming apparatus to execute determination of executability of an operation that is not determinable.