The invention provides an automatic case unpacking machine, which comprises a conveyor and a cigarette case pre-locating mechanism, a cigarette case lift mechanism, a cigarette case upright cutting mechanism, a cigarette case cross cutting mechanism, a cigarette case lower cover opening mechanism, a cigarette case upper cover opening mechanism, a cigarette case side cover opening mechanism, a cigarette pushing mechanism, a distributary output mechanism and a transverse output mechanism which are arranged on the conveyor. The invention can realize full-automatic case unpacking, and thereby, the problems of high labour intensity, low work efficiency and the like brought by artificial case unpacking in the prior art are fundamentally solved. Moreover, the automatic case unpacking machine hascompact structure, reasonable layout, accurate and rapid automatic case packing, wide applying range, convenient installation and investment saving, does not occupy more production space and can provide guarantee for the cigarette logistics distribution center to realize full-automatic operation.