A working machine comprising: a diesel engine; an exhaust treatment device having a filter (5, 6) to trap particulate matter contained in exhaust gases of the engine; regeneration control means that compulsorily elevates an exhaust temperature by allowing a certain quantity of fuel to stay in the exhaust gases of the engine to compulsorily regenerate the filter; regeneration instruction means that instructs the regeneration control means to start the compulsory regeneration; means for estimating an actual quantity of PM deposition in the filter; means in which is stored a reference quantity of deposition that indicates regeneration timing of the filter in terms of the quantity of,PM deposited in the filter; characterized in that it further comprises means for estimating a movement-associated quantity of PM likely to be deposited during movement of the working machine to a place where is suitable for the compulsory regeneration of the filter (5, 6), in the basis of a predicted value of either a time required for movement of the working machine to the place of regeneration, or a distance to the place of regeneration; means for determining whether the actual quantity of PM deposition, estimated by the actual-deposition quantity estimating means, has reached a deposition alarm level derived by subtracting the movement-associated PM deposition quantity from the reference quantity of deposition; and an alarm device for notifying an operator of a time to start the movement of the working machine to the place of regeneration when the deposition quantity estimating means determines that the actual quantity of PM deposition has reached the deposition alarm level. a diesel engine; an exhaust treatment device having a filter (5, 6) to trap particulate matter contained in exhaust gases of the engine; regeneration control means that compulsorily elevates an exhaust temperature by allowing a certain quantity of fuel to stay in the exhaust gases of the engine to compulsorily regenerate the filter; regeneration instruction means that instructs the regeneration control means to start the compulsory regeneration; means for estimating an actual quantity of PM deposition in the filter; means in which is stored a reference quantity of deposition that indicates regeneration timing of the filter in terms of the quantity of,PM deposited in the filter; characterized in that it further comprises means for estimating a movement-associated quantity of PM likely to be deposited during movement of the working machine to a place where is suitable for the compulsory regeneration of the filter (5, 6), in the basis of a predicted value of either a time required for movement of the working machine to the place of regeneration, or a distance to the place of regeneration; means for determining whether the actual quantity of PM deposition, estimated by the actual-deposition quantity estimating means, has reached a deposition alarm level derived by subtracting the movement-associated PM deposition quantity from the reference quantity of deposition; and an alarm device for notifying an operator of a time to start the movement of the working machine to the place of regeneration when the deposition quantity estimating means determines that the actual quantity of PM deposition has reached the deposition alarm level.