A low insertion force connector unit with a safety circuit unit comprising: one connector; the other connector; a driving lever rotatably and pivotally supported by the one connector, characterized in that the driving lever has an arc-shaped gear, an arc-shaped notch continued to the gear, an arc-shaped cam groove formed in the same radius from a center axis (m), and a straight groove continued to the cam groove; said low insertion force connector unit further comprises: a gear unit having a circular gear meshed with the arc-shaped gear and a spiral groove, and attached to the one connector; a first driven projection provided on the other connector, and engaged with the spiral groove; one small connector of the safety circuit unit provided on the one connector movably in a connector fitting direction; a second driven projection provided on the one small connector; and the other small connector of the safety circuit unit fixed to the other connector, wherein the one and the other connectors (2,3) are fitted to each other by meshing the arc-shaped gear with the circular gear, wherein when the connectors (2,3) are fitted to each other, the second driven projection is moved along the cam groove, and wherein when the circular gear is inserted into the notch, the second driven projection is engaged with the straight groove. one connector; the other connector; a driving lever rotatably and pivotally supported by the one connector, characterized in that the driving lever has an arc-shaped gear, an arc-shaped notch continued to the gear, an arc-shaped cam groove formed in the same radius from a center axis (m), and a straight groove continued to the cam groove; said low insertion force connector unit further comprises: a gear unit having a circular gear meshed with the arc-shaped gear and a spiral groove, and attached to the one connector; a first driven projection provided on the other connector, and engaged with the spiral groove; one small connector of the safety circuit unit provided on the one connector movably in a connector fitting direction; a second driven projection provided on the one small connector; and the other small connector of the safety circuit unit fixed to the other connector, wherein the one and the other connectors (2,3) are fitted to each other by meshing the arc-shaped gear with the circular gear, wherein when the connectors (2,3) are fitted to each other, the second driven projection is moved along the cam groove, and wherein when the circular gear is inserted into the notch, the second driven projection is engaged with the straight groove. a gear unit having a circular gear meshed with the arc-shaped gear and a spiral groove, and attached to the one connector; a first driven projection provided on the other connector, and engaged with the spiral groove; one small connector of the safety circuit unit provided on the one connector movably in a connector fitting direction; a second driven projection provided on the one small connector; and the other small connector of the safety circuit unit fixed to the other connector, wherein the one and the other connectors (2,3) are fitted to each other by meshing the arc-shaped gear with the circular gear, wherein when the connectors (2,3) are fitted to each other, the second driven projection is moved along the cam groove, and wherein when the circular gear is inserted into the notch, the second driven projection is engaged with the straight groove.