An ultrasonic transducer according to the invention includes a flexible sheet, a rigid body portion including a lower electrode made of at least a thin-film conductive material on a surface of the flexible sheet, a dividing portion which divides the rigid body portion into segments, and a plurality of transducer elements including the divided rigid body portion, has at least one transducer cell composed of one of the segments, an insulating partition portion bonded to the segment, an air gap portion surrounded by the partition portion, an upper electrode opposed to the lower electrode extending to the partition portion to sandwich the air gap portion therebetween, and an upper insulating layer formed on the upper electrode, and includes an upper protection film which continuously covers a surface portion of the transducer elements and the dividing portion.