A planar-type junction of HoBa2Cu3O7-x - La1.5Ba1.5Cu3O7-y - HoBa2Cu3O7-x having an electrode spacing as small as 0.1-mu-m is fabricated and its electrical characteristics are measured. Supercurrent through the La1.5Ba1.5Cu3O7-y layer is detected up to the temperature of 69 K. A superconducting region extends from the YBa2Cu3O7-x electrodes into a normal La1.5Ba1.5Cu3O7-y layer with a submicrometer scale. The superconducting decay length is 65 nm, which is two orders of magnitude larger than the value calculated from the conventional proximity theory.