PURPOSE: To easily demount a brake drum by demounting a connecting member which rotationally stops an adjusting bolt member and a coupling member, rotating the adjusting bolt member and thereby minimizing the projection rate thereof from a strut.

CONSTITUTION: In the case that a brake drum 1 is hard to demount at the time of maintenance or inspection of a brake device, a rotational stopping pin 10 which stops a shaft 8b of an adjusting bolt member 8 and a shaft 9b of a coupling member 9 is demounted. A returning wheel 8c of the adjusting bolt member 8 is held and rotated. A bolt 8a of the adjusting bolt member 8 is inserted into a through-hole 3a of a strut 8 irrespective of the engagement of an adjusting wheel 5 with an adjusting lever 6, and the length of an automatic adjustor mechanism is decreased. The brake drum 1 is demounted under a condition that a clearance between a second brake shoe and the brake drum 1 is enlarged.