A printhead substrate comprising a plurality of printing portions and a plurality of ink supply ports, wherein the plurality of printing portions are divided into a plurality of groups, and the plurality of ink supply ports are arranged so as to correspond to the plurality of groups respectively, the printhead substrate also comprises a plurality of first voltage wiring portions provided in correspondence with the plurality of groups, and each first voltage wiring portion includes a first wiring pattern configured to connect the first terminals of the respective printing portions in the corresponding group with each other, and a second wiring pattern connected to the first wiring pattern and arranged between an ink supply port in the corresponding group and its neighboring ink supply port.