A crossbow correction device 16 for correcting crossbow of a steel strip S by a magnetic force during conveyance includes a plurality of electromagnets 57a to 57d, 67a to 67d arranged in a strip width direction of the steel strip S and facing each other so as to sandwich the steel strip S in a strip thickness direction, a moving mechanism 51 to 54, 61 to 64 capable of moving the electromagnets 57a to 57d, 67a to 67d relative to the steel strip S, and a controller 17 configured to operate the moving mechanism 51 to 54, 61 to 64, based on a current value flowing through the electromagnets 57a to 57d, 67a to 67d.