  A tensor network formalism of thermofield dynamics is introduced. The
formalism relates the original Hilbert space with its tilde space by a product
of two copies of a tensor network. Then, their interface becomes an event
horizon, and the logarithm of the tensor rank corresponds to the black hole
entropy. Eventually, multiscale entanglement renormalization anzats (MERA)
reproduces an AdS black hole at finite temperature. Our finding shows rich
functionalities of MERA as efficient graphical representation of AdS/CFT
correspondence.
