Prostate-specific antigen (PSA) has been identified as a significant biomarker for prostate cancer screening. Heavily-doped porous silicon, etched to form a Fabry-Perot fringe pattern, can be applied to an interferometric sensing for detecting PSA bound with PSA-antibody. In the previous works, a calyx crown derivative (Prolinker-A) was used as an alternative biolinker on the porous silicon surface for interferometric biosensing of DNA-damaging chemical instead of employing the conventional biomolecular affinity method using biotin, which resulted in a denser linker formation. In this study, G5 amine-terminated PAMAM (poly amidoamine) dendrimer as a biolinker, was applied to an interferometric sensing of PSA by using porous silicon, which shows the enhancement of adhesion capability and increase of functional groups more than those with Prolinker-A. Considerably low level down to 1 ng/ml of PSA could be detected by this sensing system.