There is a short somewhere in the oven where hot is making contact with neutral or ground (the frame). This could be anywhere but the easiest thing to do is start at the plug and work your way up. Check the plug and cable for any signs of damage. If the damage is at the plug or cable then it is something you can fix pretty easily - replacement parts are easy to come by at your local hardware store.
If a quick visual inspection does not show anything you will need to start disassembling the oven and tracing the electrical connections, looking for anything damaged like nicked conductors, missing insulators, etc. If you do not have experience working on electrical components it is best to contact a qualified service technician for your appliance.
Do not use the oven until this is resolved. Do not short out the fuse or try a larger fuse.