Operation unit of engine

An operation unit is provided with an engine operation box (12) storing therein a control operation portion controlling an opening degree of a throttle valve of an engine and a start switch terminal connected to a start motor starting the engine; a throttle operating lever (11) provided in an outer portion of the engine operation box and operating the control operation portion so as to control the opening degree of the throttle valve from an idle position to a full-open position; and a start switch (14) connecting and disconnecting the start switch terminal, wherein the throttle operating lever (11) has a switch shielding portion which enables to operate the start switch (14) without an interference between the throttle operating lever (11) and an operating portion (15) of the start switch (14) at a time when the throttle operating lever (11) is at an idle position, and disables to operate the start switch (14) by shielding at least a part of the operating portion (15) of the start switch (14) by means of a part of the throttle operating lever (11) at a time when the throttle operating lever (11) is operated so as to be apart from the idle position.