The kink pair formation (KPF) process on screw dislocations in Ta was investigated by means of the anelastic creep (AEC) measurements near room temperature. The effect of σeff on HKPF and that on ν0 were investigated for σeff below 16 MPa, where σeff denotes the effective stress applied to screw dislocations responsible for the AEC through KPF, HKPF the activation enthalpy of the KPF process, and ν0 the pre-exponential factor of the inverse of the relaxation time of the KPF process. The extrapolation of the observed σeff dependence gives 2Hk = 0.97 ± 0.03 eV and In[ν0,0(s−1)] = 29.6 ± 1, where Hk denotes the enthalpy of an isolated single kink and ν0.0 is ν0 at σeff = 0. Both HKPF and ν0 show a strong decrease with increasing σeff. These features for HKPF and ν0 are very similar to those reported for Nb and Fe after the AEC measurements. We surmise that a change in the core structure of screw dislocation plays an important role for the rate of KPF on screw dislocations in the b.c.c. metals. The AEC results are discussed together with the strong decrease in HKPF with increasing σeff reported for Fe, Nb and Ta after the flow stress measurements.