Provided is a blood treatment device configured, without impairing the original function of obstruction members, in such a manner that air can easily and quickly flows in the direction of the dialysis solution outlet port of a housing (2) without staying in the space of the housing (2).In a view in the longitudinal direction of the housing (2), obstruction members (11) having a substantially circular cylindrical shape are disposed at the position where a dialysis solution inlet port (7.1) is formed and/or at the position where a dialysis solution outlet port (7.2) is formed. The obstruction members (11) each have an opening (11OP) which is formed in at least one place facing the direction of a side section (S) and which extends in the longitudinal (L) direction. Each of the openings (11O) has a proximal end opening (11OPE) having a smaller width and also has a distal end opening (11ODE) having a larger width. The distal end opening (11ODE) and/or the proximal end opening (11OPE) is configured so that the distal end opening (11ODE) and/or the proximal end opening (11OPE) has rounded sections (R) formed so as to face the directions of both side sections (S), and so that the opening degree of the opening(11OPE, 11ODE) changes gradually.L'invention concerne un dispositif de traitement de sang configuré, sans altérer la fonction d'origine d'éléments d'obstruction, d'une manière telle que de l'air peut facilement et rapidement circuler dans la direction de l'orifice de sortie de solution de dialyse d'un boîtier (2), sans rester dans l'espace du boîtier (2). Dans une vue dans la direction longitudinale du boîtier (2), des éléments d'obstruction (11) ayant une forme cylindrique sensiblement circulaire sont disposés à la position à laquelle est formé un orifice d'entrée de solution de dialyse (7.1) et/ou à la position à laquelle est formé un orifice de sortie de solution de dialyse (7.2). Les éléments d'obstruction (11) ont chacun une ouverture (11OP) qui est formée dans a
