can't reach 'Upload done'. (Upload error)

Today I tried to upload some program I made.
But.. It failed and I could see below message.

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Arduino: 1.6.6 (Windows 7), Board: "Arduino/Genuino Uno"

Sketch uses 1,788 bytes (5%) of program storage space. Maximum is 32,256 bytes.
Global variables use 200 bytes (9%) of dynamic memory, leaving 1,848 bytes for local variables. Maximum is 2,048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x31
Problem uploading to board. Seemake_clickable_callback(MAGIC_URL_FULL, ' ', 'http://www.arduino.cc/en/Guide/Troubleshooting#upload', '', ' class="postlink"') for suggestions.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x31
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x31

This report would have more information with
"Show verbose output during compilation"
enabled in File > Preferences.


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I tried to switch the COM port, use another USB cable, but every tries failed.
How can I fix it?