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The YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// co-planar Josephson junctions by Focused Ion Beam were fabricated by changing the width and the thickness of a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film. The magnetic properties of the junctions were measured at different temperatures. In the junction with 300 nm thickness, the magnetic field modulation of the critical current at 4.2 K was not observed. Near the critical temperature of the junction, the magnetic modulation curve was similar to that of a dc-SQUID. From the SEM observation, some microshorts were observed on the junction. In the junction with 200 nm thickness, the I-V curve was changed from flux-flow junction type to RSJ type. The magnetic modulation curve of the 7 /spl mu/m wide junction at 4.2 K was similar to a Fraunhofer pattern. Thus it is considered that the coupling region was changed from a microshort to weak coupling region, when the thickness of the YBaCuO film was decreased from 300 nm to 200 nm.