A collector 3 that collects particles P contained in a fluid includes: a bent pipe 31 that guides the fluid flowing from a first direction X in a second direction Z; a branch pipe 32 that causes the fluid guided in the second direction Z to branch into the second direction Z and a third direction Y; a collection pipe 34 in which the particles P in the fluid guided in the second direction Z by the branch pipe 32 are collected; and a reduction-expansion pipe 33 which is arranged between the bent pipe 31 and the branch pipe 32 and of which the flow path is narrowed while being biased to an inlet side of the bent pipe 31.