A portable working machine driven by an internal combustion engine including a carburetor (100, 250) having an intra-carburetor air passage (6, 202) receiving air filtered by an air cleaner, an output control valve (4, 204) linked to an output control operating member (Tt) operated by a user and generating a throttle opening degree corresponding to an operation of the output control operating member (Tt), a fuel discharge part (8a, 216) discharging fuel into the intra-carburetor air passage (6, 202), a fuel supply passage (8, 222) supplying fuel to the fuel discharge part (8a, 216), and a valve body (10, 230) disposed in the fuel discharge part or the fuel supply passage and driven by an electric actuator (14, 232), the valve body (10, 230) variably controlling an opening degree of the fuel discharge part or the fuel supply passage, the portable working machine comprising: a throttle opening degree detection sensor detecting the throttle opening degree; and a control unit controlling the valve body (10, 230) based on a map, wherein the map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body (10, 230) set for each section, wherein the opening degree of the valve body (10, 230) set for each of the sections is the opening degree of the valve body (10, 230) at which the engine rotation speed is highest in each section, wherein the control unit controls the electric actuator (14, 232) to achieve the opening degree of the valve body (10, 230) set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections, wherein the control unit is configured for updating, in a data updating step, the opening degree of the valve body (10, 230) set in the control map when an operation of the internal combustion engine is stable, and wherein the data updating step includes a best search process, wherein in the best search process, in the section of the control map to which the throttle opening degree in the operation state of the internal combustion engine belongs at the time of execution of the data updating step, the opening degree of the valve body (10, 230) is gradually changed to associate the opening degree of the valve body (10, 230) capable of achieving the highest engine rotational speed to the section to perform an update. a throttle opening degree detection sensor detecting the throttle opening degree; and a control unit controlling the valve body (10, 230) based on a map, wherein the map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body (10, 230) set for each section, wherein the opening degree of the valve body (10, 230) set for each of the sections is the opening degree of the valve body (10, 230) at which the engine rotation speed is highest in each section, wherein the control unit controls the electric actuator (14, 232) to achieve the opening degree of the valve body (10, 230) set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections, wherein the control unit is configured for updating, in a data updating step, the opening degree of the valve body (10, 230) set in the control map when an operation of the internal combustion engine is stable, and wherein the data updating step includes a best search process, wherein in the best search process, in the section of the control map to which the throttle opening degree in the operation state of the internal combustion engine belongs at the time of execution of the data updating step, the opening degree of the valve body (10, 230) is gradually changed to associate the opening degree of the valve body (10, 230) capable of achieving the highest engine rotational speed to the section to perform an update.