PURPOSE: To make it possible not only to properly calculate the depth of water but also to measure the temp. of water without using a lead wire, by mounting a temp. sensor part and a depth-of-water sensor part in a water temp. gange.

CONSTITUTION: A temp. sensor receiving part 11 and a depth-of-water sensor receiving part 21 are provided in a main body housing and the sensor 11 constituting the temp. sensor receiving part 1 and the sensor 21 constituting the depth- of-water sensor receiving part 2 are respectively provided so as to exposed to the outside. The temp sensor part 1 detects circumferential temp. and the depth-of-water sensor part 2 detects circumferential pressure. Next, a plurality of temp. values are preset on the basis of the program controlled by CPU3 to be stored in ROM and the pressure values in the temp. values selected from a plurality of said temp. values are detected by the sensor part 2 are the detected values are recorded on RAM5 and displayed on a display device 6. A plurality of pressure values are preset and the temp. value in the predetermined pressure value selected from a plurality of said pressure values is detected by the sensor part 1 and recorded on RAM5 and displayed on the display device 6. By this method, the depth of water can be properly calculated and, at the same time, the temp. of water can be measured.