A medical device (1) includes a main body (2) a first piercing needle (4) provided slidably with respect to the main body (2) a first holding plate (61) adapted to hold the first piercing needle (4) and provided slidably on the main body (2) and a second holding plate (62) adapted to hold a second piercing needle (3) and detachably and movably mounted on the first holding plate (61), wherein the second holding plate (62) is mounted so as to move to the first holding plate (61) in a predetermined direction.