PROBLEM TO BE SOLVED: To provide a roll baler which sets and changes setting of density of a roll bale quickly and easily.SOLUTION: A density detection device 1 includes: an opening degree detection unit 2 detecting an opening degree of a movable side half part B2 with respect to a fixed side half part B1 in a molding chamber B； an opening degree setting unit 3 setting an opening degree of the movable side half part B2 with respect to the fixed side half part B1； an opening degree comparison unit 4 comparing the opening degree detected by the opening degree detection unit 2 with the opening degree set by the opening degree setting unit 3； and an opening degree determination unit 5 determining whether or not the opening degree compared by the opening degree comparison unit 4 is a predetermined opening degree. The density detection device detects completion of the roll bale molding on the basis of a determination result of the opening degree determination unit 5.SELECTED DRAWING: Figure 7【課題】ロールベールの密度の設定及び設定変更を迅速、且つ容易に行うロールベーラを提供する。【解決手段】密度検出装置１は、成形室Ｂにおける固定側半部Ｂ１に対する可動側半部Ｂ２の開度を検出する開度検出部２と、固定側半部Ｂ１に対する可動側半部Ｂ２の開度を設定する開度設定部３と、開度検出部２が検出した開度と開度設定部３で設定された開度との開度を比較する開度比較部４と、開度比較部４で比較された開度が所定の開度であるか否かを判定する開度判定部５とを備え、開度判定部５の判定結果に基づいて、ロールベール成形が完了したことを検知する。【選択図】図７
