Hydraulic driving device for working machine

A hydraulic driving device for a working machine surely prevents behavior of a single rod double acting cylinder not intended by an operator when discharge pressure of a main pump is raised to raise exhaust gas temperature to temperature required for burning particulate matter. A selector valve (160) interposed between a spool valve (61) and a rod chamber of a single rod double acting cylinder (51) and a section (a filter regeneration time actuation valve (122), a vehicle body controller (150)) controlling the selector valve, are provided. A switch control section prevents a flow of oil directed from the rod chamber of the cylinder toward the spool valve by actuating the selector valve by a poppet of the selector valve when a by-pass cut valve (110) is controlled to increase a load of an engine (21) to a degree exhaust gas temperature reaches temperature required for burning particulate matter.