Biosensors are used in various applications such as disease diagnosis, environmental monitoring, drug development, and food safety. Recently, as the medical paradigm has changed from the treatment of disease to the diagnosis and prevention, the biosensor research related to the early diagnosis of intractable disease is actively being studied. Especially in the case of Alzheimer's disease, there is still no definitive treatment because there is no way to make an early diagnosis of Alzheimer's disease but discovered when the disease is already advanced. For early diagnosis of Alzheimer's disease, it is essential that highly sensitive sensors capable of detecting very low concentrations of biomarkers of several pM or less are essential. Transducers that convert the detection of biomaterials into electrical signals in biosensors are very important factors in increasing the sensitivity of sensors. In this paper, a biosensor was fabricated using aligned carbon nanotubes as transducer materials. Carbon nanotubes are suitable for the detection of minute changes on the surface due to their high electrical conductivity, the size of a few nanometers similar to a biomolecule, and the high surface-to volume ratio. However, since the resistance of tube-tube junction of CNT is about 10 times higher than the resistance of the carbon nanotube itself, the junction point may degrade the performance of the sensor. To solve this problem, we fabricated a biosensor with very high sensitivity and uniformity by aligning carbon nanotubes using the Langmuir-Blodgett method. The sensor has a detection limit of 139fM and 1.1fM for amyloid beta and tau protein, respectively. It is expected that the production of these sensors will provide a direction for early diagnosis of Alzheimer's disease.