The object of this invention is to improve the capacity of a caster to surmount the sectional difference by diagonal entry. The caster of this invention is characterized in comprising a wheel frame, a first wheel, and two second wheels which are smaller than the first wheel. The second wheels are mounted on the wheel frame, and respectively configured on both sides of the first wheel. If the spacing between the first wheel and the second wheel is d and the turning radius of the first wheel is , then the expression of d < is satisfied.本發明之課題,是使對段差斜斜地進入時的腳輪的越過能力提昇。解決手段,本發明是一種腳輪,其特徵為,具備:輪架;第1車輪;以及比前述第1車輪更小的2個第2車輪,其被安裝在前述輪架,且分別被配置在前述第1車輪的兩側,以前述第1車輪與前述第2車輪之間的間隔為d、前述第1車輪的回旋半徑為時,滿足d<。Z‧‧‧垂直方向X‧‧‧垂直於Z的面Y‧‧‧垂直於Z的面Q2‧‧‧中心軸C2‧‧‧旋轉軸130‧‧‧主輪140‧‧‧輔助輪E1‧‧‧線段L1‧‧‧回旋中心到輔助輪的前端的距離Q1‧‧‧中心軸C1‧‧‧旋轉軸P‧‧‧回旋中心E2‧‧‧線段L2‧‧‧主輪與輔助輪的旋轉中心的距離Q3‧‧‧中心軸S‧‧‧段差‧‧‧回轉半徑α、β‧‧‧進入角d‧‧‧間隔R、r‧‧‧旋轉半徑H‧‧‧高度
