In an operation mode controller wherein a sensor for sensing a quantity of a variable to be controlled is provided and a plurality of operation modes are changed from one to another in accordance with the sensed quantity to set any desired mode, the controller includes; a memory for setting and storing change conditions of the plural operation modes; apparatus preset for determining a set of threshold values for each of the plurality of operation modes, selecting apparatus for choosing the set of threshold values corresponding to a preset operation mode; an switching device for changing the operation modes in accordance with the change conditions when the sensed quantity of the variable that is to be controlled exceeds the chosen set of threshold values corresponding to the preset operation mode.