A connecting device (6) is provided for interconnecting a windscreen wiper device (1) of the flat blade type and an oscillating arm (7) pivotally connectable to the connecting device about a pivot axis near one end thereof. The windscreen wiper device includes an elastic, elongated carrier element, as well as an elongated wiper blade (2) of a flexible material, which can be placed in abutment with a windscreen to be wiped. The wiper blade includes at least one groove (3), in which groove a longitudinal strip (4) of the carrier element is disposed. The connecting device is arranged to be connected to the longitudinal strip, and includes—at least one hole (19) of a first type arranged to allow a welding tool access through the hole of the first type to contact the longitudinal strip for welding the longitudinal strip and the connecting device together; and—at least one hole (20) of a second type arranged to allow a pin access through the hole of the second type and through the longitudinal strip for interconnecting the longitudinal strip and the connecting device.