A precooked-food warmer for baby and diet food which is contained in an openable, rigid container comprises a housing that can be fixed to the container and in which is located an electrical heating unit. The unit is equipped with connectors such that energy is supplied to the unit and with a heat-conducting means to transfer heat from the heating unit to liquid or semi-liquid food in the container. A transfer member of a rigid heat-conducting material that is immersible in the food and is detachable from the heating unit is also provided. Preferably, the transfer member defines at least one sword-like section of large surface area that is immersible in the food.