A hydrogen generating device may include a water supply device for cartridges; a first hydrogen supply valve provided in a first hydrogen supply passage through which hydrogen gas is supplied from the first cartridge to a buffer tank; a second hydrogen supply valve provided in a second hydrogen supply passage through which hydrogen gas is supplied from the second cartridge to the buffer tank; and a main hydrogen supply passage for supplying hydrogen gas from the buffer tank to outside. For switching a hydrogen supply source from the first cartridge to the second cartridge, a controller may perform: a first process to stop supplying water to the first cartridge and supply water to the second cartridge with the second hydrogen supply valve closed, and a second process to open the second hydrogen supply valve to supply hydrogen gas from the second cartridge to the buffer tank.