Provided is an image forming system that prevents leakage of confidential data. In the image forming system, a terminal includes a confidential-data-transmitting unit, a code-image-acquiring unit, and a confidential-document-data-creating unit. The confidential-data-transmitting unit transmits confidential data specified for confidentiality inside a document of document data to a server. The code-image-acquiring unit acquires a code image for outputting the confidential data from the server. The confidential-document-data-creating unit creates confidential-document data in which the code image is added to the document data. A server includes a confidential-data-acquiring unit, a code-image-creating unit, a code-image-transmitting unit, and a code-confidential-data-transmitting unit. The confidential-data-acquiring unit acquires the confidential data that is transmitted from the terminal. The code-image-creating unit creates the code image for outputting the confidential data. The code-image-transmitting unit transmits the code image to the terminal. The code-confidential-data-transmitting unit transmits the confidential data to an image forming apparatus. An image forming apparatus includes a decoding unit, a code-confidential-data-acquiring unit and an output-data-creating unit. The decoding unit decodes the code image from the confidential-document data that includes the code image. The code-confidential-data-acquiring unit acquires the confidential data from the code-confidential-data-transmitting unit according to the contents of the code image. The output-data-creating unit creates output data in which the confidential data is included in the confidential-document data.