To enable an air velocity of sampling air to be precisely measured, a smoke detector (S) includes: a smoke detection part (22) connected to a sampling pipe (11); a fan (12) that sucks sampling air (SA) into the sampling pipe; and an air velocity sensor (15) that measures an air velocity of the sampling air within the sampling pipe. The air velocity sensor (15) is disposed at a primary side of the fan (12), and a straightening vane (25) is disposed between the air velocity sensor (15) and a suction port (12a) of the fan (12).