Electrostatic adhesion is evaluated for robotic wall climbing. To realize electrostatic wall adhesion, flexible electrodes were fabricated using plastic film and conductive foil. The wall adhesion performances were measured for conductive and non-conductive surfaces. The measurement results for a conductive surface revealed that flexible electrodes can work as a suction cup, and that both air suction force and electrostatic force can contribute to wall adhesion. A prototype robot using the flexible electrodes was fabricated, which could successfully climb up on a conductive wall with 6.6 mm/s. For adhesion to non-conductive surfaces, two additional methods were applied to the flexible electrodes, which are surface pre-charging and use of comb electrodes. The second prototype robot using the proposed methods could successfully adhere to a glass surface and could climb up with an average speed of 1.75 mm/s.