AC conductivity measurements with an impedance analyzer were carried out for a hydrogen-doped coordination polymer, N,N'-bis-(2-hydroxyethyl)dithiooxamidatocopper(II), in order to estimate the protonic conductivity (sigma(p)). The log sigma(p) was linearly increased from 2.6x10(-9) to 2.2x10(-6) S cm(-1) with relative humidity (RH) from 45 to 100% at 300 K. A slight hysteresis of protonic conductivity was observed upon increasing and decreasing RE, which implies that H3O+ is generated by a reaction between water molecule and acid-base polymer near RH similar to 100%.