There is provided a hexagonal boron nitride powder, having: an average long diameter (L50) of 3 to 20 m, an average thickness (T50) of 0.3 to 2 m, a (L90L10)/L50 of 2.0 or less, a (T90T10)/T50 of 2.0 or less, and an average aspect ratio of 10 to 30; a dynamic friction coefficient (MIU) of 0.50 or less, and a deviation of the dynamic friction coefficient (MMD) of 0.0050 or less; and a specular reflection intensity of 80 or more as measured by a goniophotometer under a condition of an angle of incidence of 60 C.