A protection monitoring circuit includes a protection circuit which detects overcharge, overdischarge, and overcurrent of a secondary battery, and a secondary battery monitoring circuit which monitors a state of the secondary battery and detects a residual quantity of the secondary battery. The protection circuit includes a first communication terminal that is connected to the secondary battery monitoring circuit, a second communication terminal that is connected to a mobile device, and a level shift circuit that is connected to the first and second communication terminals. The level shift circuit performs a level shift of a signal input of the first communication terminal so as to become a second level and outputs the signal to the second communication terminal, and also performs the level shift of a signal input of the second communication terminal so as to become a first level and outputs the signal to the first communication terminal.