PURPOSE: To eliminate a useless space and to contribute to the compacting of a work machine, by placing a heavy weight member at the inside of the folded part of an apron cover body, also guiding the heavy weight member downward obliquely toward the inner part than the end face of a bed.

CONSTITUTION: An apron cover body 3 is delivered from the end face of a bed 1 when a spindle head 4 is advanced on the bed 1 by the actuation of a reciprocating device 3. The apron cover body 5 has flexibility for the progress direction of the spindle head 4, yet, a droop part 5a is pulled downward by a heavy weight member 6, so the delivered apron cover body 5 is pulled into the lower part of the bed 1 in order. When the apron cover body 5 is thus moved, the heavy weight member 6 is moved down accordingly. The droop part 5a of the apron cover body 5 is drooped obliquely toward the bed 1 side, because of the heavy weight member 6 being guided toward the inner part than the end face of the bed 1 by a guide part 7.