A print substrate connector having a main body comprising a pair of supporting portions. A lock arm 26 is provided on a sidewall of a substrate mounting groove 22 formed in the main body of the substrate connector, into which groove 22 a terminal connecting portion 30 of the print substrate 29 is inserted. The part of the sidewall of the substrate mounting groove 22, on which part the lock arm 26 is placed, faces a vacant portion at the sides of the terminal connecting portion 30 of the print substrate 29, on which vacant portion no element is mounted. In operation or when the print substrate 29 is inserted into the mounting groove 22 of the main body, a locking claw 28 formed on the lock arm 26 is adapted to engage with a locking hole 32 formed on the vacant portion of the print conveniently used as a locking means of the substrate without a bad influence on a high density mounting of elements mounted on the substrate. A supporting foundation 34 of the lock arm 26 placed in parallel with the inner face of the sidewall of the connector main body 20a and has a forked end leaving a dent 35 on the bottom face of the forked end.