This paper proposes an intelligent Internet of Things (IoT) sensor including an analog neural network (NN) constructed using a crystalline oxide semiconductor field-effect transistor (OSFET). An analog multiply-accumulate (MAC) cell array composed of only OSFETs corresponds to a synapse circuit of each layer in the NN, and monolithically stacked OSFET layers are applicable to a multilayer NN. MAC cells execute MAC operation with current input of the order of picoamperes. Stacking a photoelectric conversion layer on the NN should achieve a low-power intelligent IoT sensor.