An image forming method includes operating, receiving, and setting. The operating includes operating in an operation mode of a plurality of operation modes. The operation modes includes a first electric power mode configured to perform an image formation process and a second electric power mode configured to consume a power less than a power of the first electric power mode and not to perform the image formation process. The receiving includes receiving a print job. The setting includes switching the operation mode to the second electric power mode after a lapse of a preset first standby period after a completion of the print job. When the print job including a sleep transition command is received in the second time slot, the switching includes switching the operation mode to the second electric power mode before the lapse of the first standby period.