To provide a connecting structure of for a plurality of pipes which can be formed in various shapes without local reduction in strength caused by welding, and can be inexpensively manufactured.

The connecting structure 101 comprises at least a first pipe 10 and a second pipe 20 connected to each other through a connector 30. The connector 30 have a first insert hole and a second insert hole for inserting the first pipe 10 and the second pipe 20, respectively, the holes extending through the connector 30 in the thickness direction thereof in a non-communicating state. The first pipe 10 and the second pipe 20 are fixed to the connector 30 by expanding the first pipe 10 and the second pipe 20 while inserting the first pipe 10 through the first insert hole in the thickness direction of the connector 30, and inserting the second pipe 20 through the second insert hole in the thickness direction of the connector 30.