The invention provides a rolling control device and a rolling control method. On the condition that mass flow plate-thickness control is carried out in a tandem rolling machine, plate speed is calculated at the output side according to forward slip so that a plate-speed meter is not acquired as much as possible, and the plate-thickness precision is prevented from reducing due to an error of forward slip. Forward slip is obtained by the condition related to rolling of a rolled material and information related to forward slip. The conveying speed of the rolled material at the output side of a first roller pair is calculated. The plate thickness of the rolled material at the output side of the first roller pair is calculated by the plate thickness of the rolled material of the rolled material at the input side of a first roller and the conveying speed of the rolled material detected by the input side of the first roller. Based on difference between the calculating result and the detecting result, the error of forward slip is calculated. Additionally, based on the above calculating result, the calculating result of the plate thickness of the rolled material at the output side of a second roller pair is corrected.