PURPOSE: To prevent frequent occurrence of water leak from bonded parts of sealing material used for joint parts in outer wall finishing material or in installing sashes of a window, a door, etc., on an outer wall, and eliminate uneven application of primer which is the most frequent cause of troubles in the sealing material especially.

CONSTITUTION: A device is composed of a primer container 1, a cap 4 for the primer container 1 provided with an inclined brush installation part 3 having a primer supply hole 2, and a rotatable brush 5 connected to the brush installation part to receive supply of primer. It is desirable to install a tube 7 for extending the primer supply hole to a corner part of a bottom part in the primer container on the cap 4 of the primer container 1, and it is desirable to compress the tube 7 to be flat at a forward end part 8, and provide it with a mark to cut it to form a specified opening at an angle part.