A `planar array transducer' with interdigital electrodes is proposed. This paper describes the structure of the transducer and experimentally investigates its behavior and realization feasibility. A transducer directivity using PbTiO3 ceramics with a large electromechanical anisotropy shows the independent behavior of an array element that consists of a few electrode finger pairs. It was found that the array transducer could be realized without cutting by using the planar structure and also that the optimum pattern ratio R (the ratio of electrode finger width to period) is about 0.5.