PURPOSE: To provide a fire detection method capable of reducing the number of fire detectors installed at respective positions to detect fire.

CONSTITUTION: First fire detectors 1a-1f, the sucking ports 2a-2f of smoke guiding pipes 3a-3f are respectively installed at the respective position to detect the fire. When detected output is supplied from the first fire detector 1a to a control part 15, by an instruction from the control part 15, smoke is sucked from the sucking port 2a at the position where the first fire detector 1a is installed and is guided through the smoke guiding pipes 3a, 3g and 11 to a shared second fire detector 14, the smoke is detected and whether it is the fire or not is decided.