The two-photon absorption of a SiC photodiode was utilized to obtain autocorrelation signals of the pulses from a mode-locked Rh6G dye laser. The autocorrelation signals were in good agreement with those obtained by a conventional autocorrelator using a second harmonic crystal and photomultiplier tube. The sensitivity of the autocorrelator with the SiC photodiode was about $4{ imes}10^3 {(mW)}^2$ . From these results it was demonstrated that the SiC photodiode is suitable as a nonlinear device for an autocorrelation measurement in the visible range.