To provide a throwaway portable toothbrush, allowing a user to easily brush his teeth, manufactured inexpensively, and not bulky when being carried.

This portable toothbrush includes: a holding grip member 10 formed of plastics to have elasticity and having a holding part 11 held by hand as a base; and a sponge layer 20 fixed to the tip 13 of the holding grip member to brush user's teeth by rubbing. The tip 13 and the sponge layer 20 are formed elliptical smoothly with dimensions suitable to be put in his mouth to brush his teeth, and in a portion extending from the tip 13 of the holding grip member to the longitudinal middle part, the holding grip member is reduced in width to form a narrow part 12. The holding part 11 has a width substantially equal to or a little smaller than the width of one indication finger, and the holding part 11 has a length to stay in hand.