A pedal holding device (12; 100; 130; 150) for holding a pedal (10; 10a; 10b; 10c) including an arm portion and an operated portion (74; 74a; 74b; 74c) such that the pedal (10; 10a; 10b; 10c) is held at the arm portion by said pedal holding device (12; 100; 130; 150), said pedal holding device (12; 100; 130; 150) comprising: a four-bar linkage (16; 102; 132; 152) including four links (40-46; 40a-46a; 40b-46b; 40c-46c) and four joints (50-56; 50a-56a; 50b-56b; 50c-56c) that connect said four links (40-46, 40a-46a, 40b-46b, 40c-46c), wherein said four joints (50-56; 50a-56a; 50b-56b; 50c-56c) include two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c) that are provided in a main body of said pedal holding device (12; 100; 130; 150), and two movable joints (54, 56; 54a, 56a; 54b, 56b; 54c, 56c) that are not provided in said main body of said pedal holding device (12; 100; 130; 150), wherein a portion of said main body which is located between said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c) serves as a fixed link (40; 40a; 40b; 40c) as one of said four links (40-46; 40a-46a; 40b-46b; 40c-46c), wherein two of said four links (40-46; 40a-46a; 40b-46b; 40c-46c) serve as two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c) each connected to said fixed link (40; 40a; 40b; 40c) via a corresponding one of said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c), wherein one of said four links (40-46; 40a-46a; 40b-46b; 40c-46c), which is not connected to said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c), serves as an intermediate link (42; 42a; 42b; 42c) that is provided with the pedal (10; 10a; 10b; 10c), and the intermediate link (42; 42a; 42b; 42c) is connected to said two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c) respectively via said movable joints (54, 56; 54a, 56a; 54b, 56b; 54c, 56c) such that the pedal (10; 10a; 10b; 10c) is not pivotable relative to said intermediate link (42; 42a; 42b; 42c), wherein an output member (60; 60a; 60b; 60c) is connected to one of said two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c), wherein said four-bar linkage (16; 102; 132; 152) is constructed such that a pivot radius of the pedal (10; 10a; 10b; 10c) is smaller when stroke of the pedal (10; 10a; 10b; 10c) is large than when the stroke of the pedal (10; 10a; 10b; 10c) is small, the pivot radius corresponding to a distance between a predetermined reference point (Pf) which lies on the operated portion (74; 74a; 74b; 74c) of the pedal (10; 10a; 10b; 10c) and a pivot center of the pedal (10; 10a; 10b; 10c) about which the pedal (10; 10a; 10b; 10c) is to be pivoted, and wherein said four-bar linkage (16; 102; 132; 152) is constructed such that an output/input ratio is smaller when stroke of the pedal (10; 10a; 10b; 10c) is large than when the stroke of the pedal (10; 10a; 10b; 10c) is small, the output/input ratio being a ratio of a force outputted through the output member (60; 60a; 60b; 60c) to an input applied to the pedal (10; 10a; 10b; 10c). a four-bar linkage (16; 102; 132; 152) including four links (40-46; 40a-46a; 40b-46b; 40c-46c) and four joints (50-56; 50a-56a; 50b-56b; 50c-56c) that connect said four links (40-46, 40a-46a, 40b-46b, 40c-46c), wherein said four joints (50-56; 50a-56a; 50b-56b; 50c-56c) include two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c) that are provided in a main body of said pedal holding device (12; 100; 130; 150), and two movable joints (54, 56; 54a, 56a; 54b, 56b; 54c, 56c) that are not provided in said main body of said pedal holding device (12; 100; 130; 150), wherein a portion of said main body which is located between said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c) serves as a fixed link (40; 40a; 40b; 40c) as one of said four links (40-46; 40a-46a; 40b-46b; 40c-46c), wherein two of said four links (40-46; 40a-46a; 40b-46b; 40c-46c) serve as two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c) each connected to said fixed link (40; 40a; 40b; 40c) via a corresponding one of said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c), wherein one of said four links (40-46; 40a-46a; 40b-46b; 40c-46c), which is not connected to said two fixed joints (50, 52; 50a, 52a; 50b, 52b; 50c, 52c), serves as an intermediate link (42; 42a; 42b; 42c) that is provided with the pedal (10; 10a; 10b; 10c), and the intermediate link (42; 42a; 42b; 42c) is connected to said two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c) respectively via said movable joints (54, 56; 54a, 56a; 54b, 56b; 54c, 56c) such that the pedal (10; 10a; 10b; 10c) is not pivotable relative to said intermediate link (42; 42a; 42b; 42c), wherein an output member (60; 60a; 60b; 60c) is connected to one of said two sub-links (44, 46; 44a, 46a; 44b, 46b; 44c, 46c), wherein said four-bar linkage (16; 102; 132; 152) is constructed such that a pivot radius of the pedal (10; 10a; 10b; 10c) is smaller when stroke of the pedal (10; 10a; 10b; 10c) is large than when the stroke of the pedal (10; 10a; 10b; 10c) is small, the pivot radius corresponding to a distance between a predetermined reference point (Pf) which lies on the operated portion (74; 74a; 74b; 74c) of the pedal (10; 10a; 10b; 10c) and a pivot center of the pedal (10; 10a; 10b; 10c) about which the pedal (10; 10a; 10b; 10c) is to be pivoted, and wherein said four-bar linkage (16; 102; 132; 152) is constructed such that an output/input ratio is smaller when stroke of the pedal (10; 10a; 10b; 10c) is large than when the stroke of the pedal (10; 10a; 10b; 10c) is small, the output/input ratio being a ratio of a force outputted through the output member (60; 60a; 60b; 60c) to an input applied to the pedal (10; 10a; 10b; 10c).