To solve a problem wherein a magnesium material is known to be inferior in plastic workability at an ordinary temperature and it is presumed that pre-annealing and warm working would be required when the magnesium material is formed into a pipe and the pipe is to be bent, but since the magnesium material is easily oxidized, it may be undesirable to carry out such heat treatment depending on the purpose of the pipe.

The bent part of the pipe 1 formed of the magnesium material is formed in double pipe structure with an inner pipe 5 inserted in an outer pipe 3. The inner pipe 5 is formed in elliptic shape, and its outer surface in the major axis direction is in pressure contact with the inner surface of the outer pipe 3. The pipe 1 is bent by a rotary draw-bending type apparatus. At this time, bending is performed by making a position adjustment so that one pressure contact side comes to a bent inside part. In this method, the pipe formed of the magnesium material can be bent without heat treatment up to a certain degree of bend radius.