Noises on dynamical systems can have positive or negative contributions. We studied the effect of additive white Gaussian noise on the phase synchronization of a coupled Hindmarsh Rose under magnetic field effect. It is found that relatively strong values of the magnetic coupling strength is needed for the system to reach complete phase synchronization in the case of noiseless neuronal network system. With the added of noise in the neuronal network, we observe an increase of the phase shit. Results showed also that noise destroys phase synchronization of the neuronal networks. Moreover, we found that for a less noising system, phase synchronization is conserved if the neuronal system already exhibited it.