To facilitate mounting work while securing sealing performance.

When the seal member is interposed between a casing 2 and a front face cover 3 in attachment of a panel instrument 1, a protrusion 5b is elastically deformed in accordance with the shape even when recesses and projections are formed on a peripheral end of a mounting opening part 4a of a panel 4, and thereby, adhesion is secured and sealing performance is improved, and an opening on an upper rear end side of the front face cover 3 is large and an inward protruding piece 5c intrudes into the inner side as shown in an upper part of Fig.2 in an enlarged state, and adhesion and sealing performance in this section can be secured.