Abstract: A sliding seat device with surrounding structure, which is applied to a bridge type machining center, includes a main body provided with a sliding portion; a sliding seat slidingly disposed on the sliding portion and reciprocating along an X-axis direction of the main body, the sliding seat provided with a housing; a sliding pillar passing through the housing and reciprocating along a Z-axis direction of the main body, one side of the sliding pillar provided with a protruding rail disposed along the Z-axis direction of the main body; an assistant plate connected with the sliding seat and facing the protruding rail; and an adjusting unit passing through the assistant plate and pushing against the protruding rail, the adjusting unit correcting a vertical bias between the sliding pillar and the main body.