The motor driving system includes a driving state amount detector configured to detect a driving state amount, a motor control part configured to perform a power supply control, a higher control part capable of outputting a higher control command to the motor control part, and a safety requesting part that inputs a safety request signal to the motor control part. The motor control part includes a motor control circuit part that performs the power supply control, a mode selecting and executing part configured to select and execute either a first safety function mode or a second safety function mode, and a comparing and monitoring processing part that compares the driving state amount and a predetermined operation monitoring pattern, when the safety request signal is inputted.