Nanbu, K. Hama, H. Hinode, F. Kashiwagi, S. Muto, T. JACoW Publishing Geneva, Switzerland Recently laser-plasma accelerators (LPAs) have attracted a lot of attention and have been developed actively toward practical applications worldwide. LPAs can accelerate electrons to high energy within a very short distance. However, its beam stability is still insufficient as compared with conventional RF accelerators. In addition, beam repetition rate is very low, consequently a beam pulse has to be diagnosed simultaneously with application. Cherenkov Diffraction Radiation (ChDR), which is the radiation generated when electrons pass near the dielectric material, will offer non-destructive beam diagnostics for LPAs. A basic experimental study on ChDR for developing a novel beam position monitor has been conducted at test accelerator facility, t-ACTS, in Tohoku University. We have investigated characteristics of ChDR from a hollow radiator and an intensity distribution of ChDR with respect to the electron beam position.