The electrostatic chuck (ESC) offers several advantages compared with mechanical holding systems because it can hold a flat object, resulting in flattening of semiconductor wafers and liquid-crystal display (LCD) panels without surface contamination and particle generation. This research tries to compute the attractive force between the Coulomb type ESC and the LCD panel using the finite element (FE) analysis and confirms the influence of the air gap upon the attractive force. The air gap exists between the LCD panel and the dielectric layer of the ESC and its effect must be considered for the accurate simulation of the force in spite of its very thin thickness. A modified FE modeling is also suggested to consider the air gap effect of ESC without meshing the air gap layer itself. The attractive force acting into the perpendicular direction of the ESC is obtained by applying the Maxwell stress tensor method and it is verified by comparison with experiment results. In conclusion, it is confirmed that the consideration of the air gap effect is essential to derive the attractive force of the ESC.