The present disclosure relates to a color image reading device that successively switches three color light sources to irradiate the color original copy and successively reads information on the original using a monochrome image sensor, and which is featured by simple construction and less reading time period. A plurality of image sensor ICs are linearly mounted. A start pulse output terminal of an anterior stage image sensor IC is connected to a start pulse input terminal of a posterior stage image sensor IC, thereby forming an image sensor block. A plurality of those image sensor blocks are provided such that start pulse input terminals of initial stage image sensor ICs in all blocks are connected together. By inputting start pulses to the terminals connected together, image signal outputs are read out simultaneously.