A switchgear operation mechanism for driving a movable contact to reciprocate so as to bring the switchgear from a closed circuit condition to an open circuit condition and vice versa, the mechanism comprising: a circuit opening spring that operates to open a circuit by discharging energy; a circuit opening trigger mechanism that maintains a state of energy accumulation of the circuit opening spring; a circuit opening operation section that releases the circuit opening trigger mechanism from constraint; a circuit closing spring that operates to close the circuit by discharging energy; a circuit closing trigger mechanism that maintains a state of energy accumulation of the circuit closing spring; and a circuit closing operation section that releases the circuit closing trigger mechanism from constraint; characterized in that at least either the circuit opening operation section or the circuit closing operation section including: an electromagnetic solenoid (60, 61) having a fitting structure provided with a step; and a solenoid spacer that adjusts a distance between the circuit opening trigger mechanism or the circuit closing trigger mechanism to be operated by the electromagnetic solenoid (60, 61) and the electromagnetic solenoid (60, 61); the electromagnetic solenoid (60, 61) having: a solenoid housing fixed by way of the solenoid spacer; a plunger (60a, 61a) slidable relative to the solenoid housing; a plunger return spring urging the plunger (60a, 61a) in a plunger returning direction; a coil rigidly fitted to the solenoid housing to drive the plunger (60a, 61a) to slide in a direction of magnetic excitation operation opposite to the plunger returning direction against the urging force of the plunger return spring by generating a magnetically excited state by electric power supplied to the coil; and a stopper fitted to the solenoid housing so as to limit sliding motion of the plunger (60a, 61a) in the plunger returning direction when no electric power is supplied to the coil, limiting position thereof being adjustable, wherein the plunger (60a, 61a) includes: a cylindrical plunger main body located facing to the coil and adapted to slide; and a step section arranged at an end of the plunger main body in a direction of magnetic excitation operation and having a diameter smaller than the plunger main body and a length defined as step size; and the solenoid housing includes: a base held in contact with the solenoid spacer and having a recess formed therein to accommodate the step section, when the circuit opening electromagnetic solenoid is magnetically excited, the length of the step section in the axial direction thereof is the step size, which is equal to the depth of the recess; and a housing main body containing the coil, the stopper being fitted to the housing main body. a circuit opening spring that operates to open a circuit by discharging energy; a circuit opening trigger mechanism that maintains a state of energy accumulation of the circuit opening spring; a circuit opening operation section that releases the circuit opening trigger mechanism from constraint; a circuit closing spring that operates to close the circuit by discharging energy; a circuit closing trigger mechanism that maintains a state of energy accumulation of the circuit closing spring; and a circuit closing operation section that releases the circuit closing trigger mechanism from constraint; characterized in that an electromagnetic solenoid (60, 61) having a fitting structure provided with a step; and a solenoid spacer that adjusts a distance between the circuit opening trigger mechanism or the circuit closing trigger mechanism to be operated by the electromagnetic solenoid (60, 61) and the electromagnetic solenoid (60, 61); a solenoid housing fixed by way of the solenoid spacer; a plunger (60a, 61a) slidable relative to the solenoid housing; a plunger return spring urging the plunger (60a, 61a) in a plunger returning direction; a coil rigidly fitted to the solenoid housing to drive the plunger (60a, 61a) to slide in a direction of magnetic excitation operation opposite to the plunger returning direction against the urging force of the plunger return spring by generating a magnetically excited state by electric power supplied to the coil; and a stopper fitted to the solenoid housing so as to limit sliding motion of the plunger (60a, 61a) in the plunger returning direction when no electric power is supplied to the coil, limiting position thereof being adjustable, wherein a cylindrical plunger main body located facing to the coil and adapted to slide; and a step section arranged at an end of the plunger main body in a direction of magnetic excitation operation and having a diameter smaller than the plunger main body and a length defined as step size; and a base held in contact with the solenoid spacer and having a recess formed therein to accommodate the step section, when the circuit opening electromagnetic solenoid is magnetically excited, the length of the step section in the axial direction thereof is the step size, which is equal to the depth of the recess; and a housing main body containing the coil, the stopper being fitted to the housing main body.