PROBLEM TO BE SOLVED: To provide a conduit diameter measurement device capable of accurately measuring a conduit diameter by appropriately filling a balloon member with liquid by easy operation.SOLUTION: A conduit diameter measurement device 100 includes a tube 10, a balloon member, a first opening 40, a second opening 50, a first flow channel 20, a second flow channel 22, and a switching mechanism 60. The first flow channel 20 and the second flow channel 22 are formed inside the tube 10, and communicate with the balloon member individually. The switching mechanism 60 is configured so as to be changeable to a first state and a second state. The switching mechanism 60 in the first state makes the first opening 40 communicate with the first flow channel 20, and the second opening 50 with the second flow channel 22 respectively, and enables the balloon member to be filled with liquid from the first opening 40 or the second opening 50. The switching mechanism 60 in the second state cuts off the first opening 40 and the balloon member, and makes the second opening 50 communicate with the balloon member.SELECTED DRAWING: Figure 6COPYRIGHT: (C)2016,JPO&INPIT【課題】容易な操作でバルーン部材に液体を良好に充填して管路径を正確に測定することが可能な管路径測定装置を提供する。【解決手段】管路径測定装置100は、チューブ10、バルーン部材、第一開口40、第二開口50、第一流路20、第二流路22および切替機構60を含む。第一流路20および第二流路22はチューブ10の内部に形成されておりバルーン部材と個別に連通している。切替機構60は第一状態と第二状態とに遷移可能に構成されている。切替機構60は第一状態で、第一開口40と第一流路20、および第二開口50と第二流路22をそれぞれ連通させて、第一開口40または第二開口50から液体をバルーン部材に充填可能とする。切替機構60は第二状態で、第一開口40とバルーン部材とを遮断し、かつ第二開口50とバルーン部材とを連通させる。【選択図】図6