Disclosed is a substrate for an electro-optical device including: a substrate; a plurality of data lines and a plurality of scanning lines which intersect with other on the substrate; a pixel electrode formed in each of a plurality of pixels which configure a display region on the substrate and are defined in correspondence with intersections between the plurality of data lines and the plurality of scanning lines; a transistor provided in each of non-opening regions which discriminate between opening regions of the plurality of pixels and including a semiconductor layer including a channel region having a channel length in one direction of the display region, a data line side source/drain region electrically connected to the data line, a pixel electrode side source/drain region electrically connected to the pixel electrode, a first junction region formed between the channel region and the data line side source/drain region, and a second junction region formed between the channel region and the pixel electrode side source/drain region; and a light-shielding section which is formed above each of the semiconductor layers, extends along the one direction, and includes a first portion which covers the first junction region and a second portion which covers the second junction region and has a width larger than that of the first portion in a direction intersecting the one direction.