RPi 3B+ with UM OS can't install PyQt5

Hey guys,
Today I want to install PyQt5 on Ubuntu Mate, but it failed. I have no idea what should I do to install PyQt5 in my raspberry pi.
Install Command: pip install PyQt5

When I use "sudo apt-get install python3-pyqt5", it succeed, but I can't import PyQt5 in python.
Could anybody help me? thx.