A side spacer structure in a connector has a side spacer mounted in a housing body having terminal receiving chambers and including a tentative retention lance for temporarily retaining a terminal inserted into the terminal receiving chambers, a securing portion for securing the terminal in a state for operation, and a terminal releasing lance is provided in a side of the tentative retention lance; wherein a front end of the terminal releasing lance is positioned backward than a front end of the tentative retention lance in an insertion direction of the connector housing.