MAST SUPPORT STRUCTURE OF TOWER CRANE AND SUPPORT METHOD OF TOWER CRANE

PROBLEM TO BE SOLVED: To provide a mast support structure of a tower crane and a support method of the tower crane capable of suppressing the addition of a vertical force caused by the moment acting on a mast to reduce a vertical setting reaction force, capable of efficiently performing a turning operation of a mast support in a narrow space, and capable of reducing a time and labor by using a pin structure as a support structure for the mast.SOLUTION: The mast support structure of the tower crane has: an upper layer support 10 which supports a vertical load and a horizontal load of the mast 3 arranged at an opening of a frame 2; and a lower layer support which supports only a horizontal load. The upper layer support 10 includes: a pair of second receiving beams 12 which are arranged at both sides of the mast 3 and supported on the frame 2; a spherical support block 13 which is arranged inside the mast 3 and provided with a spherical support 131; a support leg 14 which can be protruded from the spherical support block 13; and a spherical body block 15 has a spherical body 151 which can be fitted freely rotatably to the spherical support 131, and is detachably fixed to the mast 3 whereby the spherical support block 13 provides the mast support structure of the tower crane having such a configuration that horizontal movement with respect to the frame 2 is regulated.