A fluid visual inspection device includes a fluid visual inspection portion and one set of fastening caps. The fluid visual inspection portion includes a vane holder which has a first flange and second flange, and is coupled with a transparent duct to allow users to see vane conditions and judge whether fluid is flowing. The vane holder further has a third flange and fourth flange that have respectively an external threaded portion formed thereon screwing with the fastening caps. One end of the vane holder holds a partition to form a passage opening. Each fastening cap has one end fastened to the third or fourth flange and another end screwed with a fluid pipe. The fastening caps and the duct are not integrally formed, hence fabrication is simpler and the cost is lower and production time is shorter, and coupling of the device and fluid pipe also is easier.