Abstract: This invention relates to a nail trimmer which is adapted to operate automatically for trimming fingernails or toenails. The nail trimmer comprises a power supply means, a driving means, a switch means, a trimming means and a frame means. The power supply means, the driving means and the trimming means are mounted within the frame means in a linear relationship. The switch means is provided on the sidewall of the frame means. When the switch means is placed ON position, the trimmimg means is caused to rotate and achieve automatic trimming function as long as the trimming means is put in contact with the nail to be trimmed.