Amorphous cellulose-based tough double-network (DN) elastomers were successfully fabricated. These elastomers comprise interpenetrated poly(ethyl acrylate) (PEA) network as the soft matrix and the amorphous cellulose network as the brittle component. Unlike carbonblack-filled conventional rubbers, the obtained cellulose/PEA DN elastomers are transparent and can be dyed without any color limitation. Although the cellulose network in the DN elastomer comprises only 2.55 wt%, such cellulose network efficiently reinforces in toughness (10 times), stiffness (28 times), strength (8 times), and durability of the DN elastomer compared to the PEA elastomer. The structure and toughening mechanism of the cellulose/PEA DN elastomers are different from previously reported cellulose composites, in which cellulose nanocrystals were used simply as fillers. Upon deformation, the brittle cellulose network in the DN elastomer is ruptured sacrificially to dissipate energy, which effectively prevents crack propagation. The damaged cellulose network recovers its original structure to show recoverable mechanical properties by thermal annealing.