A soldering structure of a tubular material for soldering one end portion of a tubular material to an auxiliary plate with a soldering material coated thereto, wherein the plane auxiliary plate is formed therein with a communicating hole for allowing the tubular material to be inserted therein, one end portion of the tubular material is inserted into the communicating hole and temporarily secured to the auxiliary plate through a deformation of the auxiliary plate at the end portion of the tubular material or the peripheral area of the communicating hole before soldering, thereby to close one end of a space between the peripheral surface of the tubular material and the inner wall of the communicating hole, the space allowing the soldering material melted to be pooled therein during soldering, and the tubular material and auxiliary plate being soldered when the melted soldering material pooled in the space is hardened.