A rotating body comprising: a rotating body core; and a plurality of blades provided at an outer circumference or an inner circumference of the rotating body core at equal intervals in a circumferential direction, the plurality of blades forming a grouped blade structure in which the blades are connected over the entire circumference via an annular connection portion provided separately from the rotating body core, wherein a resonance frequency under a two nodal diameter number mode of the rotating body is lower than or equal to a rotational secondary harmonic frequency with respect to a rated rotation speed of the rotating body, characterized in that the plurality of blades are arranged so as to satisfy N d ≥ 5, wherein N d is defined as the order at which a maximum magnitude of an order component appears among order components of the following equation obtained by expressing mass distribution, rigidity distribution, or natural frequency distribution of the plurality of blades in the circumferential direction by a complex form of Fourier series, m k = M 0 + ∑ n = 1 N b M ^ n exp i ⋅ 2 πn N b k − 1, k = 1, 2, ⋯, N b where m k is mass, rigidity or natural frequency of the k-th blade, Mo is an average mass, average rigidity or average natural frequency, n is an order, M̂ n is an n-th order complex amplitude and N b is number of the blades, a magnitude of an n-th order component is defined as the absolute value of the n-th order complex amplitude M̂ n, the plurality of blades are further arranged so as to have order components each having a ratio less than 1/2, in which the ratio is obtained by dividing a magnitude of the order component by a magnitude of the component of the nodal diameter number N d. a rotating body core; and a plurality of blades provided at an outer circumference or an inner circumference of the rotating body core at equal intervals in a circumferential direction, the plurality of blades forming a grouped blade structure in which the blades are connected over the entire circumference via an annular connection portion provided separately from the rotating body core, wherein a resonance frequency under a two nodal diameter number mode of the rotating body is lower than or equal to a rotational secondary harmonic frequency with respect to a rated rotation speed of the rotating body, characterized in that the plurality of blades are arranged so as to satisfy N d ≥ 5, wherein N d is defined as the order at which a maximum magnitude of an order component appears among order components of the following equation obtained by expressing mass distribution, rigidity distribution, or natural frequency distribution of the plurality of blades in the circumferential direction by a complex form of Fourier series, m k = M 0 + ∑ n = 1 N b M ^ n exp i ⋅ 2 πn N b k − 1, k = 1, 2, ⋯, N b where m k is mass, rigidity or natural frequency of the k-th blade, Mo is an average mass, average rigidity or average natural frequency, n is an order, M̂ n is an n-th order complex amplitude and N b is number of the blades, a magnitude of an n-th order component is defined as the absolute value of the n-th order complex amplitude M̂ n, the plurality of blades are further arranged so as to have order components each having a ratio less than 1/2, in which the ratio is obtained by dividing a magnitude of the order component by a magnitude of the component of the nodal diameter number N d. where m k is mass, rigidity or natural frequency of the k-th blade, Mo is an average mass, average rigidity or average natural frequency, n is an order, M̂ n is an n-th order complex amplitude and N b is number of the blades, a magnitude of an n-th order component is defined as the absolute value of the n-th order complex amplitude M̂ n, the plurality of blades are further arranged so as to have order components each having a ratio less than 1/2, in which the ratio is obtained by dividing a magnitude of the order component by a magnitude of the component of the nodal diameter number N d.