To provide a control method for starting a blower stably and safely by taking a problem wherein air capacity of a blower on an inverter driving side becomes unstable when starting the second blower from a condition in which one blower is operated into account.

This automatic boiler controller is provided with a means for reducing opening commands to a flow rate adjusting operation end of the blower driven by an inverter in accordance with increase of opening commands to the flow rate adjusting operation end of the blower driven by commercial frequency power supply when starting the blower driven by commercial frequency power supply while the blower driven by the inverter is operated and a means for changing rotational speed of the blower driven by the inverter into rotational speed in operation by respective blowers after an opening command to the flow rate adjusting operation end of the blower driven by commercial frequency power supply reaches opening in operation by respective blowers.