Abstract: The present invention concerns a plumb-bob device for vertical pointing operation with a beam-casting housing supported vertically by a plurality of legs via a gyroscope mechanism. The device has a reduced size, so that it can be handled quickly and conveniently on a construction cite. The legs are mounted for expansion and contraction in and around an upper end portion via the gyroscope mechanism on and around an upper end portion of the housing. The legs each have an inner surface complementary to the outer periphery of the housing. The device thus can assume a shape just like a long pencil when the legs are contracted. For vertical pointing operation, the housing is held vertically by the legs in an expanded state. The device can be used as an inverted plumb-bob device and also as a pointer by mounting a retaining member, which has a string, on lower end portions of the legs in the contracted state thereof.