In order to enable supply of a sampling air to a smoke detection portion at a stable flow velocity, the present invention provides a smoke detector including: a black box (21) including a smoke detection portion (25) having an inflow port and an outflow port; a sampling pipe (30) laid in a monitor space; a gas flow pipe (P) connected to the sampling pipe and which houses a fan (3) therein; a flow path branching portion (33) provided to the gas flow pipe on a secondary side of the fan and connected to the inflow port of the smoke detection portion; and a flow path merging portion (32) which is provided to the gas flow pipe on the secondary side of the fan and connected to the outflow port of the smoke detection portion, and at which a pressure of a fluid flowing through the gas flow pipe is lower than a fluid flowing through the gas flow pipe at the flow path branching portion.