The invention relates to a detection device and method for rebar in concrete, and provides a static field capacitance principle-based low-cost, high-accuracy and nondestructive detection device and method. Various types of targeted detection are implemented on the rebar in the concrete, and an accurate and convenient detection result comprising rebar position, size and corrosion quantity is expected to be acquired, and operation efficiency of detection, building engineering acceptance and detection, reinforcement and identification of an existing rebar concrete structure are improved. The detection device comprises an electrode plate, a DC power supply and a data acquisition processing device, wherein the data acquisition processing device comprises a capacitance meter, a display module, an operation module, a processing module and a data connection line socket, wherein an angular frequency of the capacitance meter is set as 10KHz, the display module is used for displaying a numericalvalue obtained after detection of a capacitance sensor, the operation module is used for performing artificial actual operation and inputting special engineering information to set a parameter, the processing module is used for performing data analysis statistics on the numerical value measured by the capacitance meter and other relevant numerical values, and the data connection line socket is used for connecting the electrode plate.