An improved cardiotachometer comprises a transmitting section and a receiving section. The transmitting section includes a detection circuit for detecting electrocardiographic signals obtained from a pair of electrodes mounted near the heart of a human body. The transmitting section processes and transmits the electrocardiographic data with ID code data to the receiving section in the form of a radio signal. The receiving �section?! compares the transmitted ID code with a stored ID code. If the two codes do not agree, the receiving section does not make any calculations or modify the previous signal. If the two codes agree, a genuine reception has resulted and the receiving section computes a heart rate based on the electrocardiographic data. A display section displays the computed heart rate. The use of the ID code comparison method eliminates erroneous reception of signals generated by noise or interference by the receiving section.