In this paper , we loosen the zero equation of state of dark matter to a constant w _ { dm } .
By using the currently available cosmic observations which include the type-Ia supernovae , the baryon acoustic oscillation , the WiggleZ measurements of matter power spectrum and the cosmic microwave background radiation from the firs release of Planck dat through the Markov chain Monte Carlo method , we found the equation of state of dark matter in 3 \sigma regions : w _ { dm } = 0.000707 _ { -0.000747 - 0.00149 - 0.00196 } ^ { +0.000746 + 0.00146 + 0.00193 } .
The difference of the minimum \chi ^ { 2 } between the \Lambda CDM and \Lambda wDM models is \Delta \chi ^ { 2 } _ { min } = 0.446 for one extra model parameter w _ { dm } .
Although the currently available cosmic observations favor the \Lambda wDM mildly , no significant deviation from the \Lambda CDM model is found in 1 \sigma regions .