A teeth grinding preventing device to be put in an oral cavity of a user includes a main body portion formed into a substantially arcuate shape along a curve of a maxillary teeth alignment of the user and configured to cover an occluding surface of the maxillary teeth, a sensor portion embedded in the main body portion to extend in parallel to the occluding surfaces of maxillary and mandibular teeth and configured to detect an occlusal force and output a detection signal, a teeth grinding determining portion configured to receive the detection signal and determine whether or not the user is grinding the teeth, and a stimulation providing portion configured to provide the user with a stimulation when the teeth grinding determining portion determines that the user is grinding the teeth, and the stimulation providing portion is provided to be mountable and demountable with respect to the main body portion.
