This invention relates to a hollow toothbrush adapted for fluid draining comprising a brush head having a neck portion and a bristle portion disposed on the neck portion, and a hollow brush stem form a drain passage with a first opening and a second opening respectively formed at two opposite ends thereof. The neck portion is partially inserted into the drain passage through the first opening and is formed with a plurality of ribs radially extending from the neck portion to the brush stem, so as to securely fix the brush head to the brush stem by the ribs. During teeth brushing, the mixed liquid of dentifrice and saliva flows along the neck portion through the first opening into the brush stem and then flows out the brush stem through the second opening, and thereby the mixed liquid is prevented from contaminating the user's hand gripping the toothbrush.