The present invention relates to an attachment (X) for body fluid sampling device, comprising: a lancing member (21) including a lancing needle (28); an analyzing implement (5) for obtaining information on a target component in body fluid; and an attachment main body (1) holding the lancing member (21) and the analyzing implement (5). The attachment main body (X) includes a movable member (3) movable with the analyzing implement (5) longitudinally of the lancing needle (28). The attachment main body (1) includes for example, a holder (2) for holding the lancing member (21). The holder (2) has an inner space (22) for movement of the lancing needle (28). The lancing needle (28) is held preferably as sealed in the inner space (22).