The present invention is intended to improve the responsiveness while increasing a flow rate, and is an orifice having a valve seat surface, the orifice includes: a vertical channel that opens to valve seat surface and a facing surface that faces the valve seat surface; and a horizontal channel that opens to an outer circumferential surface between the valve seat surface and the facing surface, and that intersects with the vertical channel. The vertical channel is split into a plurality of channel branches from an intersection with the horizontal channel, with a space therebetween, on a side of the facing surface.