Foldable training wheel device

A foldable training wheel device comprising:

• an outer tube being hollow;
• an inner tube inserted in the outer tube, being rotatable in the outer tube, being up and down moveable in the outer tube, and having
• a riding position;
• and
• a folded position;
• a positioning module mounted on the outer tube and the inner tube to position the inner tube on one of the riding position and the folded position of the inner tube relative to the outer tube, and comprising
• a positioning unit mounted on a bottom of the outer tube, and comprising
• at least one riding recess recessed in the positioning unit;
• and
• at least one folding recess recessed in the positioning unit;
• an engagement unit mounted on the inner tube and selectively engaged in one of the at least one riding recess and the at least one folding recess, wherein when the engagement unit is engaged in the at least one riding recess, the inner tube is positioned on the riding position, and when the engagement unit is engaged in the at least one folding recess, the inner tube is positioned on the folded position;
• a restoring unit abutting between the outer tube and the inner tube;
• and
• a training wheel mounted on a bottom of the inner tube.