A reference signal generating circuit, an AD conversion circuit, and an imaging device are provided. A clock generating unit includes a delay section including delay units, each of which delays an input signal and outputs a delayed signal, and outputs a low-order phase signal based on a signal output from the delay section. A high-order current source cell unit includes high-order current source cells, each of which generates the same constant current. A low-order current source cell unit includes low-order current source cells weighted to generate constant currents having current values that differ by a predetermined proportion of a current value of the constant current generated by the high-order current source cell. Selection of the high-order current source cell is performed based on a clock obtained by dividing a clock based on the low-order phase signal.