Surface treatment device for metal

The invention relates to the field of grinding machining, in particular to a metal surface treatment device which is used for grinding a cylinder part and comprises a rack, an inner grinding mechanism and an outer grinding mechanism, and the cylinder part comprises a side peripheral wall and a top cover; the inner grinding mechanism comprises a rotating frame, a first grinding roller, a driving roller and a first adjusting assembly, and the outer grinding mechanism comprises a second grinding roller, a follow-up roller and a second adjusting assembly. The driving roller rotates along a second rotating direction and drives the side peripheral wall to rotate along the second rotating direction, the first grinding roller rotates along the first rotating direction to grind the inner surface of the side peripheral wall, the rotating frame rotates along the first rotating direction and drives the driving roller and the first grinding roller to revolve around the rotating center of the rotating frame, and the second