Discerning Android users who frequently root their devices to unlock the privilege of installing root apps, mods, custom kernels and ROMs, may sometimes notice a weird error message that reads: "Unfortunately SuperSU has Stopped" on their rooted phones.
If you ever encounter this error then you need not fret, as the issue can be fixed by simply reinstalling the SuperSU app or the SU binaries on the affected device.
Steps to fix 'Unfortunately SuperSU has Stopped' error on Android devices
Step 1: Download the latest SuperSU update package: UPDATE-SuperSU-vx.xx.zip
Step 2: Copy the zip file to your phone and flash it via any custom recovery tool like CWM or TWRP or Philz touch recovery.
Step 3: If custom recovery is not installed, just extract the SuperSU zip file to a desired location on the phone and open the extracted folder. Locate the folder named Common and copy the Superuser.apk to your phone. Enable Unknown sources option via Settings > Security and then install the APK.
Step 4: Then go to the Play Store and install the SuperSU app.
Finally, reboot your device and the Unfortunately SuperSU has Stopped error should be fixed now.
[Source: Droid Views]