Here we present telomerase activity screening using a capillary electrophoretic (CE) microdevice for human cancer diagnostics. The telomerase enzyme, a contributor to the maintenance of telomere length in cancer cells, was extracted from various human cells including MCF-7 (Human breast cancer cells), A549 (Human lung cancer cells), and SK-N-SH (Human neuroblastoma cells), and then telomeric repeat amplification protocol (TRAP)-based genetic analysis was performed to evaluate the activity of telomerase enzyme. The resultant 6-bp tandem repeat PCR amplicons derived from cancer cells were separated and detected on the 6 cm-long CE microdevice within 5 min. A limit of detection of 5 cells was achieved to analyze the telomerase activity on a CE microchip. In comparison with a conventional PAGE method, micro-fabricated CE-based analysis has many advantages in terms of high speed, low sample consumption, and high sensitive detection. The successful demonstration of telomerase activity screening on a chip implies great potential of a complete integration of a sample preparation and PCR unit in a single format for high-performance cancer diagnostics in a clinical arena.