To provide a car wash water treatment device capable of producing wash water easily washing off dirt on vehicle bodies and improving the stickiness and spread of wax, and a car washing device.

This car wash water treatment device comprises a casing 1 which has an approximately U-shaped cross section, is mounted to a water pipe 5 or water conduit through which water is supplied to the car washing device, and is being open at its top and each side which are either made of dustproof material or rendered dustproof, a yoke 2 of an approximately U-shaped cross section which is provided within the casing 1 via a spacer 3 made of magnetic shielding material, a magnetic field tunnel 15 constructed of the yoke 2 and a yoke plate 10 covering the upper surface of the yoke 2, a plurality of permanent segments 7 positioned inside the tunnel 15 in mutually opposed and appropriately longitudinally spaced relationship, a cover 8 of an approximately U-shaped cross section which covers the permanent magnets 7 while allowing the water pipe 5 or water conduit to pass therethrough, and a lid 8 for covering the open top face of the casing 1.