A sample holder includes an adapter attached to an adapter attaching part. An analysis target, e.g., analytical cell, has first electrical connection members. The adapter has second electrical connection members. The number of the first electrical connection members and the number of the second electrical connection members are the same. Further, the adapter has third electrical connection members, and the adapter attaching part has fourth electrical connection members. The number of the third electrical connection members and the number of the fourth electrical connection members are the same. For example, the third electrical connection members are six electrically conductive membranes, i.e., a first electrically conductive membrane to a sixth electrically conductive membrane. Among the six electrically conductive membranes, only the third electrically conductive membrane is not electrically connected to any of the second electrical connection members and the first electrical connection members.