Disclosed are a brake apparatus, a wheel body assembly and a rollator. The brake apparatus includes a shaft body, a housing, a magnetic induction mechanism, a rectifier mechanism and an adjustment mechanism, the housing is rotatable relative to the shaft body, the magnetic induction mechanism is used to generate resisting force opposite to a rotation direction of the housing or the shaft body by a magnetic field reaction when the housing rotating relative to the shaft body, the rectifier mechanism is used to rectify a current of the magnetic induction mechanism, the adjustment mechanism is used to adjust the magnitude of the resisting force generated by the magnetic induction mechanism. By setting the rectifier mechanism to rectify output of the multiple wires of the magnetic induction mechanism, the structure of the adjustment mechanism can be simplified, making the overall structure of the brake apparatus simpler.