The present application discloses a brush head of an electric toothbrush and an electric toothbrush. The brush head of an electric toothbrush includes a brush head assembly, a housing assembly and a quiet transmission assembly, wherein the brush head assembly includes bristles and a brush base; the housing assembly is a hollow structure having an accommodation space disposed therein, the accommodation space, at its top, is in communication with a mounting socket, and the brush head assembly is rotatably mounted within the mounting socket; and the quiet transmission assembly is disposed within the accommodation space, and comprises an oscillating shaft, a quiet sleeve and a transmission hub, the upper end of the oscillating shaft is connected to the brush base to drive the brush base to perform oscillating rotation.