A fan frame body with bypass structure and a fan thereof. The fan includes a first fan, a second fan and a bypass structure. The second fan has a second frame body correspondingly serially connected with a first frame body of the first fan, whereby a first flow way of the first frame body communicates with a second flow way of the second frame body. The bypass structure is disposed in the first flow way or the second flow way. The bypass structure defines a bypass flow way on a circumference of the first flow way or the second flow way. By means of the bypass structure, without increasing the size of the fan and without increasing the consumed power of the fan, the air volume of the fan can be enhanced.