A static transfer switch, comprising: a first contact switching means which is turned on or off according to a first driving signal to supply output power of a first power source to a load; a first semiconductor switching means connected in parallel to the first contact switching means and turned on or off according to a first gate signal to supply the output power of the first power source to the load; a second contact switching means which is turned on or off according to a second driving signal to supply output power of a second power source to the load; a second semiconductor switching means connected in parallel to the second contact switching means and turned on or off according to a second gate signal to supply the output power of the second power source to the load; and a control means for generating the first and second driving signals and the first and second gate signals, characterized in that the control means is configured to generate and transmit simultaneously the first driving signal to turn the first contact switching means on, and the first gate signal to turn the first semiconductor switching means on, such that when the first driving signal and the first gate signal are cut off, the first semiconductor switching means and the first contact switching means are turned off, and to generate and transmit simultaneously the second driving signal to turn the second contact switching means on, and the second gate signal to turn the second semiconductor switching means on, such that when the second driving signal and the second gate signal are cut off, the second semiconductor switching means and the second contact switching means are turned off. a first contact switching means which is turned on or off according to a first driving signal to supply output power of a first power source to a load; a first semiconductor switching means connected in parallel to the first contact switching means and turned on or off according to a first gate signal to supply the output power of the first power source to the load; a second contact switching means which is turned on or off according to a second driving signal to supply output power of a second power source to the load; a second semiconductor switching means connected in parallel to the second contact switching means and turned on or off according to a second gate signal to supply the output power of the second power source to the load; and a control means for generating the first and second driving signals and the first and second gate signals, characterized in that the control means is configured to generate and transmit simultaneously the first driving signal to turn the first contact switching means on, and the first gate signal to turn the first semiconductor switching means on, such that when the first driving signal and the first gate signal are cut off, the first semiconductor switching means and the first contact switching means are turned off, and to generate and transmit simultaneously the second driving signal to turn the second contact switching means on, and the second gate signal to turn the second semiconductor switching means on, such that when the second driving signal and the second gate signal are cut off, the second semiconductor switching means and the second contact switching means are turned off.