Step 1: Identify the even prime number.
Prime numbers are numbers greater than 1 having exactly two factors.
Among all prime numbers, the only even prime number is
\[
2
\]
Thus each die must show the number \(2\).
Step 2: Determine the total possible outcomes.
When two dice are rolled, the total number of possible outcomes is
\[
6 \times 6 = 36
\]
Step 3: Determine favourable outcomes.
To obtain an even prime number on each die:
First die = \(2\)
Second die = \(2\)
Thus the favourable outcome is
\[
(2,2)
\]
Hence the number of favourable outcomes is
\[
1
\]
Step 4: Compute the probability.
\[
P(\text{both even prime}) = \frac{\text{Favourable outcomes}}{\text{Total outcomes}}
\]
\[
= \frac{1}{36}
\]
Step 5: Conclusion.
Thus the probability that both dice show an even prime number is
\[
\frac{1}{36}
\]
Final Answer: $\boxed{\frac{1}{36}}$