A windscreen wiper device of the flat blade type, comprising a longitudinal strip, as well as an elongated wiper blade of a flexible material, which can be placed in abutment with a windscreen to be wiped, which wiper blade is of the flat blade type and includes at least one groove, in which groove the longitudinal strip is disposed, wherein the windscreen wiper device further comprises a connecting device for detachably connecting the wiper blade to an oscillating arm the connecting device having a substantially U-shaped cross-section, wherein legs of the U-shaped cross-section are connected to the flexible material on opposite sides thereof, wherein the legs are provided with two pairs of opposite protrusions, and wherein the protrusions for exerting a transverse force on the flexible material, thereby locally squeezing the flexible material onto the longitudinal strip.