To investigate the galloping phenomena of overhead transmission lines under ice accretion, field observations of four-bundled conductors were carried out at the Tsuruga test lines. On December 21, 2009, the galloping of overhead transmission lines with ice accretion was observed at this site. The conductors mainly vibrated in the vertical two-loops/span mode coupled with the horizontal and torsional modes. Statistically, th e range of wind speed where galloping occurred was limited for some region. The following discussion is derived as the factor. The static angle of attack increases with the wind speed. When the angle of attack increases to values that meet the Den Hartog criterion, galloping occurs. When the wind speed increases further, the angle of attack exceeds the range of values meeting the Den Hartog criterion and the oscillation amplitude decreases.