A device for detecting state-of-health (SOH) of batteries has a detection module, a computation control module and an output module. The computation control module is electrically connected to the detection module and the output module. The detection module detects voltage values of a battery at multiple test points. The computation control module converts the voltage values at the test points into a ratio and maps the ratio to a SOH value in a SOH curve of the battery indicative of a state of health of the battery and the SOH value is outputted through the output module. The present invention can easily detect the SOH of a battery within a short period of time to solve the existing problems of being time-consuming and complicated in determining the SOH of batteries and causing incorrect determination of battery capacity and additional maintenance cost.