The electrode assembly is provided with: a rod-like body 1 that extends along a predetermined axis; a substrate that is formed with a through-hole penetrating between a front surface and a back surface and attached to a fore end part of the body; and a sensor chip for electrochemical measurement, which is attached on the back surface of the substrate such that a sensing part is exposed outside from the through-hole, wherein: on the back surface of the substrate, a wiring for obtaining an output signal from the ISFET chip is formed, and the sensor chip is attached to the wiring directly or closely; and the substrate is attached with being inclined with respect to the predetermined axis of the body, and thereby the front surface of the substrate forms at least a part of a fore end surface that is inclined with respect to the predetermined axis.