The size of an air bubble formed at a single hole placed on a flat plate submerged horizontally in distilled water was investigated as functions of (1) orifice diameter, (2) flow rate of air, and (3) contact angle of water on the plate. A circular hole, diameter 0.25 mm or 0.55 mm, was created on a stainless steel plate by means of a laser beam, and the surface energy of the plate which surrounds the hole was modified by deposition of an ultrathin layer (less than 50 nm) of a plasma polymer of which surface energy was varied by the selection of monomer and deposition conditions. It was found that the contact angle of liquid water on the surface has the most important influence on the size of an air bubble which emerges through such a hole. The contact angle of liquid on the solid surface plays a key role in determining (1) spreading of contact base, (2) bubble attachment to the surface, and (3) bubble closing which leads to the detachment of a bubble from the surface. With a hydrophobic (nonwettable) surface, a bubble develops by establishing a contact base on the surface which is significantly greater (e.g., 20 time in diameter) than the size of hole due to the nonwetting nature of the surface, and the size of bubble becomes independent of the hole size within the range of flow rates investigated (0.3-50 mL/min per hole). The size of contact base decreases with decreasing contact angle and eventually diminishes at a threshold value of contact angle. The size of air bubble becomes smaller according to the reduction of the contact base. With hydrophilic (wettable) surface, of which contact angle is below the threshold value, no contact base is observed, and the size of the hole becomes the determining factor of the size of air bubble. Only in this hydrophilic surface domain (surface highly wettable by the liquid), the size of air bubble can be correlated to the size of the hole. The influence of flow rate was found to be very small in all domains investigated in this study.