The present invention relates to a biosensor capable of determining whether the sample addition amount is sufficient. The biosensor at least comprises an insulating substrate, a working electrode and a fill detection electrode. The fill detection electrode is further away from the sample supply port of the biosensor than the working electrode, and the fill detection electrode is not in contact with a sample supply channel. The biosensor of the present invention can determine whether the sample amount added to the biosensor meets detection requirements, which effectively avoids the risk of insufficient sample amount and ensures the accuracy of test results.