A single thermoelectric device designed to operate both as an igniter and flame detector for gas burners is described. Ignition is performed via heating, by Joule effect, of a conductor which can have, preferably, catalytic activity on the combustion while the flame is detected by means of a nullhotnull thermal state via the seeback effect. Both functions are obtained via control of a circuit for delivery of the power and detection and amplification of the electrical signal correlated to the flame.