I used to micom connect ADG451 1,8,9,16(in)pins
but, After turning off the +15v/-15v power, my microcomputer started to heat up. What is the reason?
Do I need a switching circuit (TR/FET) on pins 1,8,9,16?
The ADG451 IN pins have internal esd protection diodes. it is likely that you have violated the max ratings of the ADG451.
The digital inputs must be kept with in 2 volts of the supply.