To provide a yarn breakage detection device offering high detection reliability.

The yarn breakage detection device includes: a fixedly installed support member 1; an arm member 4 with its one end attached to the support member 1 in a vertically pivotable manner, which pivots as it is lifted upward by a tensile force of a yarn 3 passing through a guide member 2 disposed at the other end; a beam irradiation means 5 to irradiate, with a beam, a position to which the arm member 4 pivots down as the yarn 3 passing through the guide member 2 breaks or comes slack; and a detection means 6 for detecting that an optical path of the beam is shut off by the arm member 4. When the arm member 4 pivots down due to the breakage or slack in the yarn 3, the arm member 4 shuts off the optical path of the beam, and the detection means 6 detects that the optical path of the beam has been shut off, thereby capable of detecting the occurrence of the breakage or slack in the yarn 3 in a noncontacting manner.