An object of the invention is to provide an image scrambling apparatus and an image descrambling apparatus capable of making a communication of secrecy by scrambling a digital image signal as well as variable-length-encoding the digital image signal.A transmitting apparatus 1 DCT-encodes an image signal V2 from an A/D converter 11 by means of a DCT encoder 12, and outputs signals of D1, D2, D3, D4, and the number of zero-runs D5. When it variable-length-encodes the D2 to D5 through a variable-length encoder 13 and outputs V3, it generates a series of PN signals K2 by means of a PN generator 18 on the basis of a PN initial value K1 from a PN initial value generator 17, adds the scalar quantumizing number D1 and K2 to each other by means of an adder 19 and outputs the scrambled D1, and then gives a scrambled image signal V4 through compositing the V3 and the D1.