Hello satiz,
The fuse has to be placed before the varistor.
The varistor is there to quench any mains voltage spikes and transients within the tolerance of the fuse. i.e. The fuse will blow, thus minimizing any damage that may be sustained by the varistor.
Varistors used in any design should be replaced after x amount of years. Why? Their molecular structure changes over time due to spikes etc. In my early X-Box days, I've had to replace the varistors in many an X-Box PSU, due to them virtually exploding, and in some rare instances, causing the PSU to catch fire.
I would recommend you encase your varistor with heat-shrink tubing. This will minimize the chance of a fire and cosmetic damage to other nearby components.
Regards,
Relayer