To provide a fluid mixer capable of reducing pressure loss securing desired excellent performance by the dispersing feed of a second fluid into a first flow path.

A fluid mixer 6 is arranged between a first flow path A1 and a second flow path A2 which is in parallel with the first flow path A1 in which the second fluid flows and feeds the second fluid in the second flow path A2 to the first fluid in the first flow path A1 by dispersion, wherein the fluid mixer 6 is provided with a plurality of feeding holes 8 arranged inside the first flow path A1 dispersing in the direction of the width of the first flow path which is in the leaving direction from the second flow path A2 and a plurality of feeding paths 9 independently conducting the second fluid from the second flow path A2 to each of the plurality of the feeding holes 8.