In this work, we manipulated recombinant yeast cells onto a sensing electrode by using hydraulic and electrophoretic force; and thus the current response of trace enzyme activity was increased in p-aminophenyl- β -D - galactopyranoside (PAPG) solution. The recombinant yeast which can generate β-D -galactosidase (β- Gal) in response to steroidal hormone 17 -estradiol were employed as the sensing element of the developed cell-based biosensor. Cells was trapped and stabilized within a microwell structure when they flowed through the sensing electrode. A vertical trapping force was generated by applying +2.0 V across the sensing electrode and an Indium Tin Oxide (ITO). The geometrical electrode area ( 100 × 30 μm2) was defined by a photoresister layer. Since the treated cells were collected on the electrode surface, PAP concentration can be significantly changed around the sensing electrode. Consequently, the detection limit was extend to 0.5 ppb, and the response time was shorten as fast as 15 min by using this device.