Thank you. You are right. Thw water leak is a little bit far from the spot. 1st night, I shut off main water switch and clear all water in pipes. Next morning, almost dry. 2nd night, I shut off main water switch and just clear water in washer machine's pipe. Next morning is still wet. So I guess probably the sink beside the washer machine.
We cut off a hole behind the washer machine and inside is dry; cut a hole behind sink, found the water from upper through a frame. We guess a T-way pipe cross sink and washer machine pipe. So cut a holeat the cross, it is water leak in the T-pipe.
Thank you very much for all help.