An air conditioner comprising: a cross flow fan with an axial direction, a left-right direction being defined to be parallel to the axial direction; and a stabilizer and a rear guider which are provided on respective sides of an outer periphery of the cross flow fan to form an air passage, wherein at least one of the stabilizer and the rear guider comprises a protruding portion, wherein the direction in which the protruding portion protrudes is defined as the height; wherein at a leading end portion of the protruding portion, level-difference portions (28a-28e; 928a-928e, 929a-929e) are formed to be lined up in an axial direction; wherein there are parts of the leading end portion between the level-difference portions (28a-28e; 928a-928e, 929a-928e), wherein either the height of each part between neighboring ones of the level-difference portions (28a-28e) gradually changes in the axial direction, or wherein the height of each part between two neighboring ones of the level-difference portions (928a-928e, 929a-929e) is constant in the axial direction; wherein the opposing end portions in the left-right direction of neighboring parts are different in height; and wherein the level-difference portions (28a-28e; 928a-928e, 929a-929e) include first level-difference portions (28a, 28b, 28c; 928a, 928b, 928c, 929c, 929d, 929e) each of which decreases in height in the axial direction toward a central part of the fan in the axial direction and second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e) each of which increases in height in the axial direction toward the central part of the fan, characterized in that: a variation in height (ΔH1) of at least one of the first level-difference portions (28a, 28b; 928a, 928b, 929d, 929e) within a predetermined length in the axial direction is equal to a first predetermined value which is smaller than a variation in height (ΔH2) of each of the second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e). a cross flow fan with an axial direction, a left-right direction being defined to be parallel to the axial direction; and a stabilizer and a rear guider which are provided on respective sides of an outer periphery of the cross flow fan to form an air passage, wherein at least one of the stabilizer and the rear guider comprises a protruding portion, wherein the direction in which the protruding portion protrudes is defined as the height; wherein at a leading end portion of the protruding portion, level-difference portions (28a-28e; 928a-928e, 929a-929e) are formed to be lined up in an axial direction; wherein there are parts of the leading end portion between the level-difference portions (28a-28e; 928a-928e, 929a-928e), wherein either the height of each part between neighboring ones of the level-difference portions (28a-28e) gradually changes in the axial direction, or wherein the height of each part between two neighboring ones of the level-difference portions (928a-928e, 929a-929e) is constant in the axial direction; wherein the opposing end portions in the left-right direction of neighboring parts are different in height; and wherein the level-difference portions (28a-28e; 928a-928e, 929a-929e) include first level-difference portions (28a, 28b, 28c; 928a, 928b, 928c, 929c, 929d, 929e) each of which decreases in height in the axial direction toward a central part of the fan in the axial direction and second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e) each of which increases in height in the axial direction toward the central part of the fan, characterized in that: a variation in height (ΔH1) of at least one of the first level-difference portions (28a, 28b; 928a, 928b, 929d, 929e) within a predetermined length in the axial direction is equal to a first predetermined value which is smaller than a variation in height (ΔH2) of each of the second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e). wherein at least one of the stabilizer and the rear guider comprises a protruding portion, wherein the direction in which the protruding portion protrudes is defined as the height; wherein at a leading end portion of the protruding portion, level-difference portions (28a-28e; 928a-928e, 929a-929e) are formed to be lined up in an axial direction; wherein there are parts of the leading end portion between the level-difference portions (28a-28e; 928a-928e, 929a-928e), wherein either the height of each part between neighboring ones of the level-difference portions (28a-28e) gradually changes in the axial direction, or wherein the height of each part between two neighboring ones of the level-difference portions (928a-928e, 929a-929e) is constant in the axial direction; wherein the opposing end portions in the left-right direction of neighboring parts are different in height; and wherein the level-difference portions (28a-28e; 928a-928e, 929a-929e) include first level-difference portions (28a, 28b, 28c; 928a, 928b, 928c, 929c, 929d, 929e) each of which decreases in height in the axial direction toward a central part of the fan in the axial direction and second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e) each of which increases in height in the axial direction toward the central part of the fan, characterized in that: a variation in height (ΔH1) of at least one of the first level-difference portions (28a, 28b; 928a, 928b, 929d, 929e) within a predetermined length in the axial direction is equal to a first predetermined value which is smaller than a variation in height (ΔH2) of each of the second level-difference portions (28d, 28e; 929a, 929b, 928d, 928e).