A coating machine and its oven unit, comprising an overall frame with upper and lower layers, the lower layer of the overall frame is provided with a circulation pipe, a heating system, and a fresh air outlet communicating with the air return port, and the upper layer of the overall frame is provided with an upper air chamber and a lower air chamber. The side of the overall frame is equipped with a circulating fan and a static pressure box. After the hot air is blown out from the upper air chamber and the lower air chamber to dry the substrate, part of the air is discharged from the exhaust port, and the other part of the air enters the circulation pipe through the return air port, mixes with the fresh air entering the circulation pipe from the fresh air port, and is heated by the heating system It is hot air, driven by the circulating fan, the hot air enters the static pressure box, and then enters the upper and lower chambers from the air inlet of the upper and lower chambers, and repeats the above to form a circulating air, which solves the problem of the prior art. There is a dead angle problem in the wind field, and the circulating air is smoother, which can evenly dry the substrate, reduce heat loss, save costs, and improve production efficiency.