PURPOSE: To prolong the service life of a band saw blade as well as to check its vibration to the utmost by installing an opposed saw blade insert, guiding and supporting a side face of the band saw blade, in a saw blade housing freely approaching and separating, and setting up a chamber, supplying a fluid, at the supporting side.

CONSTITUTION: In order to hold a band saw blade 21 almost vertically with a workpiece supported by a work table, a pair of saw blade guides 25, 27 are installed in a beam member attached to a saw blade housing freely adjustable, while a pair of saw blade inserts 49, 51 for guiding and supporting a side face 21b of the band saw blade 21 are installed in two insert support parts 39, 41 installed at the underside of the guide base 29, and the saw blade insert 49 is made shiftable in the longitudinal direction to approach or separate from the saw blade insert 51. Two chambers 65, 67 are provided for feeding each support surface of these saw blade inserts 49, 51 with cutting oil, and these chambers are connected to a coolant tank via a pump and a filter.