We use the dense HectoMAP redshift survey to explore the properties of 104 redMaPPer cluster candidates .
The redMaPPer systems in HectoMAP cover the full range of richness and redshift ( 0.08 < z < 0.60 ) .
Fifteen systems included in the Subaru /Hyper Suprime-Cam public data release are bona fide clusters .
The median number of spectroscopic members per cluster is \sim 20 .
We include redshifts of 3547 member candidates listed in the redMaPPer catalog whether they are cluster members or not .
We evaluate the redMaPPer membership probability spectroscopically .
The scaled richness ( \lambda _ { rich } / S ) provided by redMaPPer correlates tightly with the spectroscopically corrected richness regardless of the cluster redshift .
The purity ( number of real systems ) in redMaPPer exceeds 90 % even at the lowest richness ; however , there is some incompleteness .
Three massive galaxy clusters ( M \sim 2 \times 10 ^ { 13 } M _ { \odot } ) associated with X-ray emission in the HectoMAP region are missing from the public redMaPPer catalog with \lambda _ { rich } > 20 .