The band is provided with a first band member and a second band member attached to an instrument main body, and a linking member. Each of the band members is provided with an expanding section that expands along a band extension direction, the expanding section having pliability, and having first slits having a pair of slits lying along the width direction and a slit lying along the band extension direction, and a pair of second slits lying along the width direction to communicate with the outside of the expanding section. A linking member is provided with a fixed member; a sliding member capable of sliding along the band extension direction of the first band member and provided with a linking section (projecting rod) for linking with the second band member; and an urging member for urging the sliding member in the opposite direction from the band extension direction.