© 2017. The American Astronomical Society. All rights reserved. The 1-70 keV persistent spectra of 15 magnetars, observed with Suzaku from 2006 to 2013, were studied as a complete sample. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at ≳10 keV with the 15-60 keV flux of ∼1-11 × 10-11 erg s-1 cm-2. The hard X-ray luminosity Lh, relative to that of a soft-thermal surface radiation Ls, tends to become higher toward younger and strongly magnetized objects. Their hardness ratio, updated from a previous study and defined as ξ = Lh/Ls, is correlated with the measured spin-down rate P as ξ = 0.62 × (P/10-11ss-1)0.72, corresponding to positive and negative correlations with the dipole field strength Bd (ξ ∝ Bd1.41) and the characteristic age τc (ξ ∝ τc-0.68), respectively. Among our sample, five transients were observed during X-ray outbursts, and the results are compared with their long-term 1-10 keV flux decays monitored with Swift/XRT and RXTE/PCA. Fading curves of three bright outbursts are approximated by an empirical formula used in the seismology, showing a ∼10-40 day plateau phase. Transients show the maximum luminosities of Ls ∼ 1035 erg s-1, which are comparable to those of persistently bright ones, and fade back to ≲1032 erg s-1. Spectral properties are discussed in the framework of the magnetar hypothesis.