We investigated caustic-like spin wave beams radiated from a narrow waveguide to a continuous film using a Permalloy. For this purpose, we developed a spatially resolved optical heterodyne detection of propagating spin waves by using the polar Kerr effect, which allows the measurement of the intensity and the phase information of the spin waves. We characterized magnetostatic surface spin wave modes in one-dimensional (1D) propagation and caustic-like spin wave beams in two-dimensional (2D) propagation as a function of excitation frequency. The fast Fourier transformations of the real space images reconstruct 1D and 2D spin wave dispersion, which agree with the theoretical calculations.