The present application relates to a driving machine. The driving machine has a driver blade for striking a fastener and a nose portion having formed therein an injection passage which slidably guides the driver blade, and into which the fastener is fed to be injected therefrom. An injection hole from which the fastener is injected is specified at a leading end in an injecting direction of the injection passage. The injection hole is defined by a first guide portion and a second guide portion which is movable relative to the first guide portion so as to change a cross section, perpendicular to the injecting direction, of the injection hole. A positioning apparatus is provided to dispose the second guide portion at a plurality of positions relative to the first guide portion.