Lactose-free products or low lactose content are developed for consumers with intolerance or sensitivity to lactose. Currently, the efficiency of the lactose hydrolysis process is certified by chromatographic or spectrophotometric analytical methods. However, both techniques are difficult to apply on the industrial routine, so it is necessary to develop new techniques that have agility, selectivity, sensitivity, stability and low economic cost. These characteristics can be incorporated into the development of electrochemical biosensors. The objective of this work was to develop a stabilized biosensor based on the enzyme lactase for the detection of lactose. The electrochemical measurements were performed using a potentiostat (μAUTOLAB Type III). The electrochemical cell consists of the reference electrode (Ag / AgCl), the auxiliary electrode (platinum wire) and working electrode (biosensor) on which the graphite, carbon nanotube (CNT) and lactase (Lactosyl, APSEN) were deposited. The sensitivity of the biosensor was 18.1 μA ppm-1 cm-2 considering the electrode area of 0.14 cm2 and it was also observed the increase in the stability of the system from the introduction of CNT in the graphite paste, since after 10 hours of use the variation of the signal (current) went from 16 μA (sensor graphite + enzyme) to 3,5 μA (graphite sensor + enzyme + CNT), demonstrating that the association of the enzyme with the CNT favors the electrochemical system, characteristics that demonstrate the potential for the development of an analytical device of simple industrial application in the quantification of residual lactose in dairy products.