We demonstrate a photonic crystal cavity with a tapered waveguide and a point defect to highly confine terahertz waves.The terahertz wave is first guided into the tapered waveguide,gradually compressed to its end,and finally confined in the point defect cavity.Numerical simulations with the finite-difference time-domain method indicate that the narrow band terahertz wave is highly confined in the point defect cavity with a quality factor of 5323.The demonstrated device may be used as an antenna for enhancing light-matter interactions in the point defect cavity at terahertz frequencies and may improve the sensitivity of terahertz near-field microscopy.