Abstract: Provided are a potentiometric biosensor (100) and a method for detecting urea concentration in a sample. The potentiometric biosensor (100) comprises an indication electrode (23) and a reference electrode (24). A second reaction reagent on the indication electrode (23) comprises a urease but does not comprise an electron transporter. A first reaction reagent on the reference electrode (24) comprises an electron transporter but does not comprise a urease. In the case where no external voltage is applied, after a blood sample has been added, the urease catalyzes the reaction of urea in the sample, thereby causing a potential difference between the indication electrode (23) and the reference electrode (24). Furthermore, the potential difference between the indication electrode (23) and the reference electrode (24) is in a linear relationship with the urea concentration in the sample, and the urea concentration in the sample can be calculated according to such linear relationship.