To provide a method of toppling a tower structure more safely, simply and quickly than in the conventional manner. In a method of toppling a tower structure that is fixedly supported on a base 20 to demolish the tower structure 10, the method includes a base dividing step of dividing the base 20 into an upper base 22 and a lower base 26, by cutting the base 20 in a substantially horizontal direction, an upper base dividing step of dividing the upper base 22 into a support base portion 23 and a separated base portion 24 by cutting the upper base 22, in a longitudinal direction, from above to a substantially horizontal surface 20a, a removing step of removing the separated base portion 24, and a toppling step of toppling the tower structure 10 together with the support base portion 23 using, as a tumble axis 23a, a lower edge of a longitudinally cut surface 22a of the support base portion 23, in which the tumble axis 23a is located on a toppling direction side of the tower structure with respect to a center of gravity C. Thus, since the tumble axis 23a of the robust base serves as a tumble fulcrum by itself, there is no possibility that breakage of the base is caused even by the concentration of a buckling load, and the tower structure can be toppled in an intended direction.