To improve the conventional portable toothbrush set to be a tooth- brushing tool housing case of a portable fountain pen type.

The tooth-brushing tool housing case of the portable fountain pen type consists of a toothbrush housing case obtained by providing a space part in the main body of the shape of a fountain pen to house a toothbrush and a tube containing tooth paste in the space part and screwing an opening part with a stopping cap, and an opening and closing cap obtained by screwing an opening and closing cap with an attaching and detaching pin to the other end of the toothbrush housing case. In a method for using the tooth-brushing tool housing case of the portable fountain pen type, the main body of the tooth- brushing tool housing case is always carried mounted in the pocket of a garment such as a men's suit to freely brush the teeth by taking out the tooth-brushing tool housing case from the pocket any time and any where a user desires to do and the main body of the tooth-brushing tool housing case is disposable after the use.