To cut continuously inner and outer faces of a bamboo of at least 20 cm length having its circumference at least cut into two in the longitudinal direction regardless of whether joints are or not on the inner and outer faces.

The height and the width of divided faces are formed by a fixed blade 32 and a rotating blade 33 with the bottom of a bamboo 1 as a reference, and the inner face including inner joints are cut roughly by a cutting tool close to the sectional shape of the bamboo 1, and the bamboo is finished into the given inner diameter by a cutting tool planted on the end of the circumference of a circular plate, and then the bamboo including the outer periphery is finished into the given outer diameter by a cutting tool planted on the inner peripheral end of the annular circular plate. The bamboo is processed by a device with a supporting section combined with a V-shaped roller so that the bamboo 1 is not moved other than in the forward moving direction in respective processes.