An in-plane-type channel-drop filtering device with input/output waveguides and a point defect cavity in a two-dimensional-photonic crystal slab is investigated. The in-plane operation becomes possible by employing a point defect cavity with an extremely high Q factor to suppress the radiation loss-for the out-of-plane direction. 60degrees bends are-also introduced in the output waveguide to avoid interference between the input/output waveguides. The transmission frequency range of the output waveguide with-bends is tuned by changing the size of the air holes at the apex of the corner so that the resonant frequency of the point defect cavity is-within the transmission band. A channel drop operation with a very high resolution of 0.12 nm is successfully observed at 1.55 mum wavelengths. (C) 2004 American Institute of Physics.