A construction machine having a device for attaching and detaching a counterweight according to the present invention comprises a lower traveling body; an upper rotating body mounted rotatably on the lower traveling body; the upper rotating body having a support bed standing out from a rear part thereof; and a device for attaching and detaching a counterweight mounted on the support bed. The attaching and detaching device comprises a telescoping device having a lower end pivotally connected in the vicinity of the support bed, a restiform body suspended through a guide portion provided on the telescoping device; and oscillating structure for oscillating the telescoping device around the lower end as fulcrum. The oscillating structure displaces the telescoping device extended from a substantially vertical attitude to an inclined attitude when the counterweight is detached. According to the present invention, an inclined bed is not required, and locating of the counterweight to the support bed can be done easily.