To provide an opening mechanism in an opening device for bale-broken raw cotton, capable of preventing the remaining of ridge portions formed using press bars and capable of uniformly opening the raw cotton over the whole surface of the raw cotton, because the raw cotton portions inserted into opening blades and compressed with the press bars are left without being opened on the opening of the raw cotton, and further because the residual raw cotton portions cause troubles such as a trouble in which the opening work is interfaced.

This opening device for bale-broken raw cotton is provided with an opening mechanism 3, which is moved and simultaneously sequentially scrapes the fed bale-broken raw cotton. Therein, the opening mechanism 3 has a scraping member 5 and a member 10 for moving the scraping member 5. In the scraping member 5, rotated opening blades 7 for scraping and press bars 9 for pressing the raw cotton are alternately disposed. Auxiliary press members 15 having a small inclination angle to the movement direction of the scraping member 5 due to a movement member are protectedly attached to the lower raw cotton press surfaces of the press bars 9.