projectedly provided on the tip end of the tension lever 29 and tension is imparted to the ink ribbon by guiding the ink ribbon by the guide pin 35 a cut away portion 36 is formed around the central hole 30 of the tension lever 29 and in the mounted state of the ribbon cassette the knurled portion 28 of the supply core 26 protrudes from the cut away portion 36 a convex portion 37 is formed adjacent to the cut away portion 36 designated by 38 is a lock pawl rotatably supported on a pivot boss 39 formed on the lower case 4 in its mounted state a spring portion 40 which is a part of the lock pawl 38 is fixed to the stop portion 41 of the lower case 4 and acts to bias the lock pawl 38 counterclockwise as viewed in fig2 a guide portion 42 is formed on the tip end of the lock pawl and is urged against the convex portion 37 of the tension lever 29 by the force of the spring portion 40 a pawl portion 43 is formed at the center of the lock pawl 38 and meshes with the knurled portion 28 of the supply core 26 denoted by 44 is a take up lever which is pivotally supported on the lower case 4 by a cylindrical portion 45 being fitted to the rotary shaft 46 of the lower case 4 reference numeral 47 designates a torsion coil spring wound on the cylindrical portion 45 and having one end thereof stopped by the stop portion 48 of the take up lever 44 and having the other end stopped by the stop portion 49 of the lower case 4 the take up lever 44 is.