An assembly of a working vehicle and a front loader, the front loader including a pair of main frames, a pair of coupling frames, a pair of booms and a bucket and being configured to attach the booms to the working vehicle; each main frame supporting a corresponding boom via a corresponding coupling frame and including a first frame and a second frame; the first frame having a first support part having a first support surface that is oriented on a first virtual plane and is fixed to one portion of a vehicle body; and a second support part having a second support surface that is oriented on a different virtual plane from the first virtual plane and is fixed to another portion of the vehicle body; wherein the first and second virtual planes (P1, P2) are vertical to the left-right direction of the vehicle body; the first frame is configured such that the first support part and the corresponding portion of the vehicle body are mutually fixed at the first support surface, and the second support part and the corresponding portion of the vehicle body are mutually fixed at the second support surface; and the first frame further comprises a third support part: formed in a plate shape, having a front side surface arranged vertically to the front-back direction of the vehicle body, and fixed to a front upper end of the second support part; characterized in that the first frame is further configured such that the front side surface of the third support part is located in a portion of the vehicle body different from portions which the first and second support surfaces (111a, 112a) are fixed to. the front loader including a pair of main frames, a pair of coupling frames, a pair of booms and a bucket and being configured to attach the booms to the working vehicle; each main frame supporting a corresponding boom via a corresponding coupling frame and including a first frame and a second frame; the first frame having a first support part having a first support surface that is oriented on a first virtual plane and is fixed to one portion of a vehicle body; and a second support part having a second support surface that is oriented on a different virtual plane from the first virtual plane and is fixed to another portion of the vehicle body; wherein the first and second virtual planes (P1, P2) are vertical to the left-right direction of the vehicle body; the first frame is configured such that the first support part and the corresponding portion of the vehicle body are mutually fixed at the first support surface, and the second support part and the corresponding portion of the vehicle body are mutually fixed at the second support surface; and the first frame further comprises a third support part: formed in a plate shape, having a front side surface arranged vertically to the front-back direction of the vehicle body, and fixed to a front upper end of the second support part; formed in a plate shape, having a front side surface arranged vertically to the front-back direction of the vehicle body, and fixed to a front upper end of the second support part; characterized in that the first frame is further configured such that the front side surface of the third support part is located in a portion of the vehicle body different from portions which the first and second support surfaces (111a, 112a) are fixed to.