A hybrid-type working machine comprising: an automotive vehicle body (2, 3) provided with a working mechanism; an engine that is disposed on said vehicle body (2, 3) and drives a hydraulic pump; a first electric motor that is driven by said engine to generate power or assists in a drive of said engine by supply of power; an electricity storage device that stores power generated by said first electric motor or discharges power therein; a second electric motor that is driven by power supplied from said electricity storage device or supplies regeneration power generated by a regeneration operation to said electricity storage device; a first inverter for controlling an operation of said first electric motor; and a second inverter (55,) for controlling an operation of said second electric motor, wherein said first inverter and said second inverter are mounted on a support bracket elastically supported on said vehicle body (2, 3) in a position different from a position where said electricity storage device is mounted, said first inverter and said second inverter are connected by a connecting line in which a cooling medium for cooling said first inverter and said second inverter circulates, said support bracket, said first inverter, said second inverter and said connecting line are configured as an inverter assembly, an inlet line is connected to one inverter of said first inverter and said second inverter, said inlet line causing the cooling medium for cooling said first inverter and said second inverter to flow into said one inverter, and an outlet line is connected to said other inverter, said outlet line causing the cooling medium having cooled said first inverter and said second inverter to flow out, a plurality of cables (50, 51, 59, 60) are connected respectively to said first inverter and said second inverter, said support bracket is provided with cable fixing tools (41A, 41B, 44A, 44B) for fixing said plurality of cables (50, 51, 59, 60) respectively and line fixing tools (39A, 39B) for fixing said inlet line and said outlet line respectively, characterized in that said support bracket comprises: a lower side mounting member that is positioned in a lower side in an upper-lower direction and on which one inverter of said first inverter and said second inverter is mounted, and an upper side mounting member that is positioned in an upper side from said lower side mounting member and on which the other inverter is mounted. an automotive vehicle body (2, 3) provided with a working mechanism; an engine that is disposed on said vehicle body (2, 3) and drives a hydraulic pump; a first electric motor that is driven by said engine to generate power or assists in a drive of said engine by supply of power; an electricity storage device that stores power generated by said first electric motor or discharges power therein; a second electric motor that is driven by power supplied from said electricity storage device or supplies regeneration power generated by a regeneration operation to said electricity storage device; a first inverter for controlling an operation of said first electric motor; and a second inverter (55,) for controlling an operation of said second electric motor, wherein said first inverter and said second inverter are mounted on a support bracket elastically supported on said vehicle body (2, 3) in a position different from a position where said electricity storage device is mounted, said first inverter and said second inverter are connected by a connecting line in which a cooling medium for cooling said first inverter and said second inverter circulates, said support bracket, said first inverter, said second inverter and said connecting line are configured as an inverter assembly, an inlet line is connected to one inverter of said first inverter and said second inverter, said inlet line causing the cooling medium for cooling said first inverter and said second inverter to flow into said one inverter, and an outlet line is connected to said other inverter, said outlet line causing the cooling medium having cooled said first inverter and said second inverter to flow out, a plurality of cables (50, 51, 59, 60) are connected respectively to said first inverter and said second inverter, said support bracket is provided with cable fixing tools (41A, 41B, 44A, 44B) for fixing said plurality of cables (50, 51, 59, 60) respectively and line fixing tools (39A, 39B) for fixing said inlet line and said outlet line respectively, characterized in that said support bracket comprises: a lower side mounting member that is positioned in a lower side in an upper-lower direction and on which one inverter of said first inverter and said second inverter is mounted, and an upper side mounting member that is positioned in an upper side from said lower side mounting member and on which the other inverter is mounted. a lower side mounting member that is positioned in a lower side in an upper-lower direction and on which one inverter of said first inverter and said second inverter is mounted, and an upper side mounting member that is positioned in an upper side from said lower side mounting member and on which the other inverter is mounted.