An image forming apparatus having a normal mode and a power save mode in which power consumption is reduced more than in the normal mode, characterized by: a slave controller configured to perform first processing or second processing different from the first processing in a return from the power save mode to the normal mode; a master controller configured to return the slave controller from the power save mode to the normal mode; a printing section configured to execute a print job; and a detection section connected to the slave controller and configured to sense a state of the image forming apparatus, wherein the master controller is connected to the slave controller through a signal line and is configured to output to the slave controller a return request from the power save mode to the normal mode in a manner to change a level of the signal line, in order to make the slave controller perform the first processing after output of the return request, the master controller is configured to set the level of the signal line at a predetermined first level, and in order to make the slave controller perform the second processing after the output of the return request, the master controller is configured to set the level of the signal line at a predetermined second level, the slave controller is configured to determine, on the basis of the level of the signal line after the output of the return request, which processing is to perform, the first processing or the second processing, when the slave controller receives an instruction to perform one of the first processing and the second processing from the master controller, the slave controller is configured to allow the printing section to perform a warm-up operation necessary for execution of the print job, and when the slave controller receives an instruction to perform the other of the first processing and the second processing from the master controller, the slave controller is configured to allow the printing section not to perform the warm-up operation and to notify the master controller of information indicating the state of the image forming apparatus detected on the basis of an output from the detection section. a slave controller configured to perform first processing or second processing different from the first processing in a return from the power save mode to the normal mode; a master controller configured to return the slave controller from the power save mode to the normal mode; a printing section configured to execute a print job; and a detection section connected to the slave controller and configured to sense a state of the image forming apparatus, wherein the master controller is connected to the slave controller through a signal line and is configured to output to the slave controller a return request from the power save mode to the normal mode in a manner to change a level of the signal line, in order to make the slave controller perform the first processing after output of the return request, the master controller is configured to set the level of the signal line at a predetermined first level, and in order to make the slave controller perform the second processing after the output of the return request, the master controller is configured to set the level of the signal line at a predetermined second level, the slave controller is configured to determine, on the basis of the level of the signal line after the output of the return request, which processing is to perform, the first processing or the second processing, when the slave controller receives an instruction to perform one of the first processing and the second processing from the master controller, the slave controller is configured to allow the printing section to perform a warm-up operation necessary for execution of the print job, and when the slave controller receives an instruction to perform the other of the first processing and the second processing from the master controller, the slave controller is configured to allow the printing section not to perform the warm-up operation and to notify the master controller of information indicating the state of the image forming apparatus detected on the basis of an output from the detection section.