tank a sub tank that receives the machining liquid that overflows from the machining tank a slit that is provided in an end wall of the sub tank for allowing a connection member to pass through the connection member connecting the ascent descent machining tank and the ascent descent device and a seal that is arranged in a gap between the ascent descent machining tank and an inner wall of the sub tank and prevents the machining liquid in the machining tank from leaking out into the sub tank application_number US 201414781449 A description exemplary embodiments of a wire electrical discharge machining apparatus which is presented as an electrical discharge machining apparatus according to the present invention will be described in detail below with reference to the drawings the present invention is not limited to the embodiments fig1 is a longitudinal sectional view schematically illustrating an embodiment of a wire electrical discharge machining apparatus according to the present invention fig2 is a perspective view schematically illustrating the shapes of a machining tank and an ascent descent machining tank of the wire electrical discharge machining apparatus according to the embodiment fig3 is a longitudinal sectional view schematically illustrating the shapes of the machining tank the ascent descent machining tank and a sub tank of the wire electrical discharge machining apparatus according to the embodiment in fig2 a workpiece a surface plate and a machining liquid are omitted additionally a sub tank 26 which wraps around the outer periphery of the wire electrical discharge.