The invention provides an extensible article carrier on a bicycle. The extensible article carrier comprises a support plate, a plurality of connecting columns arranged on two sides of the support plate, and extension frames arranged on the connecting columns in a sleeving manner; each of the extension frames comprises a transverse rod, wherein a plurality of sleeve columns corresponding to the connecting columns are arranged on the transverse rod; a connecting hole is formed in one end of each of the sleeve column in a concave manner, and the shape of each connecting hole is matched with the corresponding connecting column. According to the extensible article carrier on a bicycle disclosed by the invention, the width of the article carrier can be adjusted, so that the article carrying area of the article carrier is enlarged, and when the article carrier is used for carrying articles with large sizes, the articles can be guaranteed to keep stable, and are not liable to drop off. When the article carrier is not used, the article carrier can be contracted to normal size, so that the using space is reduced.