To attain the miniaturization, weight reduction and cost reduction of an apparatus itself by preventing an increase in bending cost by the circulating use of a large amount of water-soluble lubricant supplied when bending a metal tube, and pressurizing and jetting the large amount of water-soluble lubricant at high pressure without using a pump of high output.

A water-soluble lubricant supply means includes: a pressure boosting means that has a cylinder part for reciprocating a rod supported into a hollow part of a pressurizing part slidably in an axial direction and pressurizes the water-soluble lubricant after vacuum-sucking the water-soluble lubricant stored in a tank, into the pressurizing part in association with the reciprocating movement of the rod; a mixing means for mixing compressed air into the water-soluble lubricant pressurized by the pressure boosting means, to increase pressure; and an opening/closing means provided at a bending mandrel and allowing the water-soluble lubricant to be jetted into the metal tube when the water-soluble lubricant supplied from the mixing means has at least required pressure.