We are now conducting a systematic survey for high-z (z>3) protoclusters using the extremely wide imaging data produced by the Subaru/Hyper Suprime Cam. The goal of the HSC protocluster survey is to trace redshift evolution of cluster galaxies up to z~6 with very high number statistics (10 - 20 protoclusters per redshift bins at z > 2) as well as to see a possible variety of protoclusters(~1000 protoclusters at z~4) at the same redshift. We applied an effective method to find significant overdense regions of g-dropout galaxies at z~4 based on a high surface number density. We have found 179 protocluster candidates with more than 4-sigma overdensity significance over 107 deg2 of the initial HSC data release for the wide layer. I will report the current status of the survey and initial results.