Why yes, it so happens there is a word for it:

triskaidekaphobia \tris-ky-dek-uh-FOH-bee-uh\, noun:
a morbid fear of the number 13 or the date Friday the 13th
--triskaidekaphobic, adjective and noun; triskaidekaphobe, noun

Triskaidekaphobia is a fairly new word (first found in print in 1911) formed from Greek treiskaideka, triskaideka, thirteen (treis, three + kai, and + deka, ten) + phobos, fear.

There are many theories about the origin of triskaidekaphobia. In medieval Christian countries the number 13 came to be considered unlucky because there were 13 persons at the Last Supper of Christ. Fridays are also unlucky, because the Crucifixion was on a Friday. Hence a Friday falling on the thirteenth day would be regarded as especially unlucky.

Some famous triskaidekaphobes*:
* Napoleon
* Herbert Hoover
* Mark Twain
* Richard Wagner
* Franklin Roosevelt

* Source: "It's just bad luck that the 13th is so often a Friday," Electronic Telegraph, September 8, 1996