An inter-frame encoding/decoding equipment for television signals consists of inter-frame encoding equipment encoding a difference between television signals and the output of a frame memory and inter-frame decoding equipment which receives an encoded signal sent from the inter-frame encoding device via a transmission line, which decodes by adding the output of the frame memory to the encoded signal. The inter-frame encoding equipment is provided with a first operation circuit which operates the remainders obtained by dividing, by a predetermined value, the number of bits of logic "1" in the bit groups into which the output or the input of the frame memory is divided by a predetermined unit. The inter-frame decoding equipment is provided with a second operation circuit which operates the remainders obtaiend by dividing, by a predetermined value, the number of bits of logic "1" in the bit groups into which the output or the input ot the frame memory is divided by a predetermined unit. The inter-frame decoding equipment is further provided with a comparator circuit which compares and checks the values operated by the first and the second operation circuits to detect a transmission error.