The invention relates to the ultrasonic honing technology, in particular to an outer-circle ultrasonic honing device. The outer-circle ultrasonic honing device aims at solving the problem that an existing ultrasonic honing device cannot carry out outer-circle processing on diameter-variable long-shaft-type workpieces. The outer-circle ultrasonic honing device comprises a supporting part and a processing part. The supporting part comprises two horizontal guide rail pairs, a lower horizontal base plate, an upper horizontal base plate, a supporting vertical plate, a left limiting vertical plate,a right limiting vertical plate, a lower annular vertical plate, a lower inverted-U-shaped vertical plate, a left L-shaped connecting plate, a right L-shaped connecting plate, two telescopic rods, anupper annular vertical plate, an upper inverted-U-shaped vertical plate, two upper horizontal lug plate sets, two lower horizontal lug plate sets, two upper fastening bolts, two lower fastening bolts,two upper fastening nuts and two lower fastening nuts. The processing part comprises a lower transducer, a lower amplitude-change pole, a lower section of disc, a lower oilstone base, lower oilstonestrips, an upper transducer, an upper amplitude-change pole, an upper section of disc, an upper oilstone base and upper oilstone strips. The outer-circle ultrasonic honing device is used for ultrasonic honing.