A vehicular indoor temperature sensor is disclosed, which includes: a PCB substrate; a tip sensor unit connected to a front side of the PCB substrate, and which includes a first temperature sensor for detecting the temperature of the outer surface of one side of a tip housing, and a solar radiation sensor for sensing the amount of solar radiation incident on the outer surface of the one side of the tip housing; and a sensor housing, which accommodates at least a portion of the tip sensor unit and at least a portion of the PCB substrate so as to prevent foreign substances from flowing into the PCB substrate from the outside, wherein the lower side of the top of the sensor housing has a cut portion which enables foreign substances flowing in between the tip housing and the sensor housing to be discharged at the lower side.