To economically achieve capacity increase of a suction strainer.

This suction strainer 10 filtrates water from an emergency interception water source for a nuclear power plant. A strainer flange (water intake) 11, a connection tube 12, a disk 13 and one or more porous cylinder(s) 14 are arranged in series on respective axes. A reinforcement cylinder 15 arranged on an axis of the one or more porous cylinder 14 or inside or outside of a connection part thereof, a connection disk 16 inside of a tip of the porous cylinder 14, a porous cone 17 of which large diameter part is arranged inside of the connection disk 14 and of which small diameter part is arranged on a strainer flange (water intake) side, and a closure plate 18 on a tip of the porous cone 17 are included.