To provide a breaking device for parting a hard fragile plate such as a glass plate along a scribe line on a surface, capable of simplifying a structure, shortening a working time, and dispensing with a reversing operation of the hard fragile plate.

A channel cross section is expanded by supplying the pressurized fluid to a closed channel mounted in the direction along a breaking line, and the bending force or the impact force is acted on the hard fragile plate to break the plate. A structure wherein a fluid pipe 4 is stored in a groove 3 formed on an upper face of a table for fixing the hard fragile plate, or a structure wherein an opening of an upper face of the groove 3 is closed by a sheet or trip-shaped flexible plate can be applied to the closed channel. The upward movement of the fluid pipe and the flexible plate can be optionally allowed to act on the hard fragile plate through a breaking blade 10.